Chapter Text
“Wha…? Where…?”
That was all Flowey could say as he blinked at his surroundings. He was alive. Somehow. But hadn't he died? The glint of a blade tearing through his flower body…ripping apart petals, stem, and leaves over and over until… He shuddered. Yep. He definitely remembered the dying. And the fear. And the pain. And the promise of someone he once cherished. The memories slowly trickled back to him. Chara had slain everyone in the Underground, truly living their “kill or be killed” mindset that Flowey had adopted. And Chara planned to do the same to the humans who lived on the surface.
“N-No hard feelings about back then, r-right?” Flowey had said, trembling from pure terror as Chara raised the knife they had used to kill that lazybones Sans just minutes prior. “I-I'm on your side!”
Chara had smiled at him, kneeling down to his level and brushing his petals with a surprising gentleness despite the thick layer of blood and powder coating their hand. “Of course not, Asriel. I could never hate you. We're best friends. We always will be.”
“S-So, you won't…?”
The smile faded. “I have to. You promised me, Asriel. Remember the plan? How we'd break the barrier and free everyone? I can't do it without you.”
“B-But—!” He didn't want to die. He didn't want to be alone. He didn't want to say goodbye to Chara again. Not when they were right there in front of him after all this time.
“This world is cruel. It's awful. I hate it. I want it gone. But for the world to be erased, I need to become a god. And for me to become a god, everything and everyone in the Underground has to go. Including you.”
Flowey gulped when the knife was pointed at his face.
“I have to, Asriel,” Chara repeated, their voice shaking along with their grip on the weapon. “It's the only way we can have a happy ending. Monsterkind will never find peace in this world. They'll be hunted down. Killed. Forced to live in fear. The humans will do what they always do and ruin everything because they hate anything that they can't control. Someone with enough determination could just reset everything the moment they don't like the outcome they get. Mom and Dad… You… Everyone has suffered enough. I'm going to end it. And you… You're gonna be their new beginning, okay?”
Flowey was confused. “Huh? What do you mean?”
“Your soul is gone. You're an empty vessel. Everyone's souls… You can take them with you into the new world I send you to once this one is dead. Monsterkind can start fresh. And if there are humans there, you can just take seven of their souls and change that world for the better. Don't let what happened to us happen to anyone else, Asriel. Promise me that.”
“I…” Flowey paused, unsure. “But if you do this, what will happen to you?”
Chara shook their head sadly. “I'll cease to be once this world is erased. But that's okay. I had my time. I got to spend it with you, Asriel. And I'll always cherish that time we shared together.”
Golly… Even if he couldn't feel love or compassion, the words still hurt. But this was Chara's last wish. He would honor that wish, just as he did the first time. Back then, it was to be returned to the golden flowers of their childhood home. Now, it was to make their shared dream a reality. A dream of monsters and humans living together in harmony.
“Okay…” Flowey took in a deep breath, steeling himself. “Okay. I'm ready. If that's what you want, I'll do it. I'll make it happen. I promise, Chara.”
Chara smiled again, tears running down their face as they pressed the knife into his cheek. “Thank you, Asriel. Thank you for everything. For being my friend. For supporting me. I hope in the next life…that you'll find someone to cherish as much as you did me.”
The knife ripped into him.
And then he was here. Wherever here was. On the surface. With healthy trees and blue sky and fluffy clouds that reminded him of his mother and father's fur. With a gentle breeze that made his petals and leaves sway. With a bright light warming his face. It was…beautiful. As beautiful as Flowey remembered it being. This was what monsters had been denied for so long. This was what the humans had taken away from them when they sealed monsterkind beneath Mt. Ebott. And now, it was up to Flowey to bring about the resurrection of monsterkind.
Somehow.
He…actually wasn't sure how he was going to do that. Sure, Chara's suggestion of claiming seven human souls and becoming a god and simply bending reality to his will would be the easiest and most direct solution. But what if there were no human souls to claim? He'd have to find some sort of way to put a monster soul into a living vessel of some kind. Every monster soul he had only amounted to the same level of power that one human soul possessed. That level of magic wouldn't be enough to form or build a monster body from scratch.
And even if there were humans in this new world…Flowey wasn't sure if he even wanted to become a god anymore. Chara was gone for good this time. He couldn't reset the timeline back to before they died. He couldn't bring them back from the world they had destroyed. He couldn't play with them ever again. All he had now was Chara's last wish. His purpose beyond that…he'd have to figure it out. He could feel it immediately. That power to go back to a specific point and try again so long as he was determined to change an outcome? It didn't exist here, as Chara hoped. There would be no resets in this world. No do-overs. So Flowey could not afford to fail.
With determination burning within the hollow core where his soul should be, Flowey dug through the earth. Time to see what this new world had in store for him.
Kill or be killed.
It seemed like that mindset rang true even in this new world. Flowey watched from afar for months. No matter where he was in the land, the humans actively fought each other. They aimed to kill in every skirmish. They used a strange kind of magic that originated from the center of their being that let them breathe fire, move earth, bend water, control wind, and summon electricity. They gleefully spilled blood and painted the land red with it. They murdered children without mercy. And for what? A perceived victory and glory for their group's name. Meaningless objective gains at the cost of loved ones’ lives. Disgusting. This was why Chara hated the human world. This was why Chara wanted to destroy everything. And Flowey didn't blame Chara one bit for feeling that way after seeing the carnage for himself in this world. If he knew this was what human nature was at its core, then maybe he should have let Chara kill the humans that attacked them back then. And yet…Chara was different. Humans like Chara existed. Humans who were nice and silly and loved deeply and would look at a monster and see a friend instead of a foe.
Where were those types of humans? Were they even allowed to exist in this cruel world? Was this world filled with so much death and devastation that such souls had to be disposed of? Perhaps. Things were looking grim for his plan. Humans were the ideal vessels Flowey could use to bring monsterkind back. With a human's physical form, a monster could come back stronger than they were before in their magic-composed bodies and they wouldn't have to fear that their very beings would turn to dust should any human with ill intent threaten them. Reanimating dead human bodies wouldn't work due to the fact that, by the time the human soul passed on and ceased to be, the body would no longer be functional. And Flowey couldn't entrust a monster soul to just any living human. They had to be understanding. Open-minded. Patient and kind. Violent intentions and dominant wills would threaten the existence of a monster's soul and then the human soul would just override and erase it. If Flowey couldn't find suitable human vessels, then he would have no choice but to steal human souls, create a magic-composed body for each monster soul with his godly powers, and reshape the world himself. And he really didn't want to build up a world by himself. He wouldn't even know what to call it! “New World” was too plain. Although, his dad would probably like it.
He snapped out of his thoughts when he sensed the vibrations of trampling feet through the earth. Someone was approaching. Several someones, in fact. He dove through the ground, deciding to hide at the base of the forest trees. He waited and watched as the vibrations increased in frequency and strength. And then, a shadow flew by his vision. It was a mere blur, moving so fast that Flowey would've missed it if he had blinked. Several more blurs flew by, following after the first blur he saw. Intrigued, Flowey gave chase.
This was sure to be interesting. And interesting it was, Flowey found out.
It was tough to keep up with the targets that the pursuers were chasing. A young man with shockingly bright white hair, clad in blue armor adorned with a collar of equally white fur. A young black-haired child, no older than three years, was clutched tightly in his arms. A bunch of rugged-looking ruffians, armed to the teeth with blades and empty containers like they were planning to take the remains of their prey like a reward. The white-haired one was heavily injured, blood trailing down his face and soaking the fabric of his shirt and pants. Yet, despite being hurt, his attention was focused solely on protecting the kid he was carrying.
Flowey followed the two, nearly losing sight of them once the adult leapt into the trees and crossed the branches with a strange type of grace only seen in one who was familiar with the landscape. For almost a half hour, the young man fled until he almost missed his landing on yet another branch. His expression twisted in pain and frustration, crimson eyes flitting about as if to catalogue his surroundings. He jumped down, sprinting towards a cave hidden by the underbrush of the forest. Flowey smirked. No human could run forever. Now was his chance to observe. Creeping closer, Flowey kept his senses alert. He heard strained panting from within the darkness.
“Damn it…” a deep voice cursed.
“H-Hey? Y-You okay?” the child's voice, full of terror and worry, asked. “You're hurt really bad.”
A pause. The deep voice softened. “…I'll be fine. Don't worry.”
Pointless assurance. The adult was in bad shape. He was in no condition to keep running and those men following him were still out there, searching for their prize.
“Why?”
“Why what?”
“Why did you save me?” The child clarified. “You're a Senju. You're the White Demon.”
“Yes. And?”
“And I'm an Uchiha. So why…?”
“Why did I choose to save you from those bloodline thieves, even though our clans are sworn enemies?” The man finished. “That's simple. It's because I don't see an enemy when I look at you. I see a child being forced to fight for his life. When I look at you…I see my younger brothers. My little brothers who died before me…who I couldn't protect or save when they needed me. I couldn't let that fate happen to you too, even if you are an Uchiha. Even if you may grow up someday to face me on the battlefield.”
Flowey perked up at the words.
“…They’re still out there. I can sense them,” the so-called White Demon muttered. “I'm going to be honest with you. The odds are unfavorable, but there is a chance you can get out of this situation alive with your eyes still in your skull. I'm going to distract them. As soon as I engage, you run. You keep running towards your clan's territory and don't look back. Izuna and the others will find you, I promise.”
“B-But that's suicide! There was, like, twenty of them chasing us! You'll die! They won't leave a shred of your corpse behind if it means they can somehow steal the Wood Style kekkei genkai from your body! Even if you don't have it, they won't care!”
“I am a shinobi. It's an unfortunate fact that any day could be our last. If my last moments must be today, so be it. This outcome is acceptable.”
“But you're Tobirama Senju! You're the Senju clan head's brother! If you die because you were protecting me—!”
“My brother will not seek vengeance,” the man, Tobirama apparently, replied resolutely. “Kagami, I believe it was? You don't know my brother like I do. He has always had a soft heart, unwilling to see the shadows cast by this world that he only sees light in. Even now, he desires peace between our clans. I've long accepted that my importance to him compared to an old friendship is…negligible. If anything, my potential death should increase the probability of a ceasefire if the Uchiha believe they have a better standing in terms of power.”
Wow. Just…wow. This guy was willing to trade his life for an enemy if it meant their survival. This guy believed he wasn't worth crying over if he died. This was actually hard to listen to, even if Flowey couldn't feel any sort of compassion for him. Underneath the cold logic, this Tobirama person was speaking from a place born from kindness and selflessness. He wanted a child to live. He was putting someone else's happiness first. He was sacrificing his future so others could have one. He didn't fear death—no, he looked it in the eye and stood firm. Now that was determination. In a way, he reminded Flowey of Chara. And that was…ideal. He finally found a human vessel that could work.
Maybe—just maybe, if he pushed the human a little farther—a monster soul could replace the human soul and claim the body for itself if the human soul was weakened enough? The human was hurt pretty bad already. But for this test, it'd have to be a powerful monster soul in case the human soul fought back to keep control. Flowey grinned widely. He knew exactly who to stuff into that human's body. Time to make an entrance!
What a mess. Then again, it was his own fault he ended up in this situation in the first place. First that unfortunate encounter with that Uchiha platoon, led by Izuna of all people, while on what was supposed to be a relatively harmless scouting mission on the borders between Uchiha and Senju territory. At least their brief skirmish had informed Tobirama of the pressing circumstances the Uchiha had been in. They weren't there to invade Senju lands. They had been tracking a foul party of bloodline thieves that had recently stolen several children from various different clans in the area, including Izuna's youngest cousin Kagami. Tobirama should have let things be. Bloodline thieves didn't kill right away unless the kekkei genkai was easily stolen from the body. It was an Uchiha child that was kidnapped, which meant as soon as the eyes were removed the child would be killed. He shouldn't have cared. Yet, his cursed soft heart refused to fall before that logic. Uchiha or not, a child was in danger. He imagined if Kawarama or Itama were in Kagami's place and his decision was made long before his senses flared, scanning the land to locate the foreign chakra that had dared to sully Senju lands with its presence.
Tobirama found their little hiding spot easily. The problem was getting Kagami back to the Uchiha unscathed after he had invaded their hideout. The Uchiha couldn't venture further into Senju territory without risking further conflict, which would only slow down their rescue mission. And those bloodline thieves were smarter than Tobirama gave them credit for, making sure their full force hadn't been congregated in that one spot. Tobirama couldn't fight with his full power while protecting a child as young as Kagami, so fleeing was his only option.
And now here he was, injuries from fighting both Izuna and the bloodline thieves slowing him down. His stamina and chakra levels were dwindling. His head felt fuzzy from blood loss. The odds of his own survival were slim. But despite that, he couldn't give up. Kagami needed him. Hashirama would weep for him. The Senju would lose one of their strongest soldiers. He couldn't die today.
“Howdy!” Tobirama reacted before the voice fully registered in his head. Shuriken went flying, embedding into the stone wall of the cave and barely missing a golden-petaled flower that certainly was not there seconds prior. The flower eyed the weapons with wide eyes—flowers did not have eyes, let alone faces—and trembled violently in fear. It looked scared. “H-Hey! All I said was a hello! What kind of psycho throws sharp pointy objects at innocent bystanders!?”
Kagami looked absolutely stunned, pointing at the plant. “I didn't know flowers could talk.”
“They don't,” Tobirama answered tersely, not dropping his guard for an instant. It may have looked harmless, but it was an anomaly. An unknown factor. No way to know if it had good intentions or sinister ones. “Who or what are you?”
The flower took a moment to regain its composure. It smiled at them, but it felt…off. Not genuine in the slightest. Tobirama's skin prickled uncomfortably while he was under the gaze of the strange plant. “I'm glad you asked nicely instead of throwing knives at me again. I'm Flowey! Flowey the Flower! Nice to meet ya. I was passing through the area—just doing as flowers do and trying to find the best place to settle down my roots without getting destroyed by humans—when I saw you fly over my head. I got curious about what was happening and decided to follow. And I noticed that you two seem to be…in a predicament.”
“It's being handled,” Tobirama stated, covering Kagami's mouth before the little one could give away anything. His instincts were screaming at him. Don't trust this thing. Not safe. Wrong. What kind of being names itself something so on the nose if they weren't something dangerous?
“Ya sure? Doesn't look that way to me,” Flowey replied with a raised eyebrow, that eerie smile still on its face. “From what I can see, you're gonna die if you go out there and fight. And if you die too soon, the brat is just gonna follow you into hell. What a waste that would be after you went through the trouble of protecting him!”
Kagami was shaking in his arms, his little hands clutching the fabric of his sleeves as if that alone could keep Tobirama here and alive with him. “What do you want?”
“The important thing here is not what I want. It's what you want,” it replied, grin growing more malicious by the second. “Your determination. That fire that burns deep within you. The power that keeps you moving forward, no matter the obstacle that stands in your way. It's what can save you both. But your determination alone won't be enough if you want to live. Your methods are too…well, let's just say they're too cowardly.”
That statement irked him. “Cowardly?”
“I mean all this fuss about how your chances aren't good or the odds aren't in your favor! That's just a fancy way of saying you give up!” Flowey explained derisively. “Your mind says no when your soul says yes! They clash and it diminishes your power! It'll hold you back and it will kill you. You need to forgo that mindset and let the full force of your determination push through! Only then will you win! Only then will you survive another day to do it all over again!”
“That's—!” Illogical. Foolish. Sure to lead to certain death in this shinobi world where one miscalculated move could spell your undoing. And yet…it had a point. Hadn't he just been thinking about how he couldn't allow himself to die, even though it could lead to positive outcomes? Was that what the flower was talking about?
“Ah hah! See? You understand,” Flowey said when Tobirama didn't respond back. “But the problem here lies with the fact that you'll falter. You think I can, but I shouldn’t because. You need to think I can, so I have to and I will! And I think I can help you there.”
Kagami pulled Tobirama's hand away from his mouth, eyes sparking alight with hope. “Really? Can you help us?”
“Kagami—”
Kagami turned his head up towards Tobirama, his own determination blazing. “If it can help you live, then you should accept the offer! If you die, then I won't ever be able to thank you for saving me! I won't be able to face you in honorable combat like you and Izuna do!”
Flowey raised an eyebrow again, as if expecting Tobirama to deny Kagami's wish. Tobirama let out a sigh, knowing he'd be pestered either way. He hated making decisions on a whim. There were too many unknown variables and there wasn't enough time to analyze them all. He had no idea what this “Flowey” truly wanted with him and he didn't trust the flower at all. No one ever did someone a favor out of the goodness of their hearts—nobody but Hashirama was that stupid. But there were some absolutes. Tobirama would likely die if he fought with the bloodline thieves. Kagami would be hunted down the moment Tobirama perished. The only way to stop that from happening was to not die. And if this Flowey creature could give him an advantage that would lead to that outcome, then it would be in his best interest to accept—consequences be damned.
“If I accept your help, what will you do?” Tobirama tentatively asked.
“Nothing sinister, if that's what you're thinking,” Flowey replied. “I'm just gonna give your magic and your determination a little boost, is all.”
“My…magic?” Tobirama repeated, a little perplexed. “You mean my chakra?”
“If by that you mean the power you use to breathe fire and control water, then yes. I can kinda sense it when humans use it. Your body isn't made of ‘chakra’, but it flows through the body, right?”
“Yes.”
“Okay, good! Having that confirmed will make this easier.” Something shimmered in the air before Flowey as it was summoned forth. Something white, fraying at the edges as if trying to hold itself together. It looked like a heart that was placed upside down. “This right here? This is gonna be your new best friend. I'm just gonna merge this with your chakra. Once that happens, you should get a burst of power. You won't yield. Those humans will fall before your might. Your chakra itself will probably become even more powerful than it was before.”
“What is it exactly?”
Flowey somehow moved the thing away from Tobirama like he was a child reaching for something he shouldn't have. “I thought you were gonna drop the questions by now and just go with it. You're hesitating again. You can't hesitate or you'll die. I thought we established that already.”
He was about to argue when he felt the brush of several chakra signatures at the edge of his senses, drawing closer to their location. Flowey knew it too as it dangled the white, reversed heart before him.
“Time's a wastin’. Make your choice, human. Kill or be killed; which do you prefer?”
Hesitation versus determination. Risk versus gains. Do or die. This clashed with everything he was; everything he had learned since he first picked up a kunai and began his training to be his family's sword and shield. Tobirama was the knowledge and clarity to Hashirama's passion and fortitude. He didn't make decisions like this lightly. But the enemy was near. He had to make a choice now, regardless of how much he didn't trust this flower.
He was determined to live and save Kagami. That answer would have to be enough.
“I choose to kill.”
“Good.”
The heart shot towards him, thrust right through the center of his chest where it sank through armor and through flesh. The impact alone sent him flying into the wall, making him drop Kagami in the process. He felt sick as something forcefully struck what felt like the core of his being—like it was trying to erase who he was. With every passing moment, his being was ripped apart and stitched back together. With every attack, it happened. Over and over and over again. It wouldn't relent, but neither did he. He couldn't break. He couldn't falter. He refused to. If he did, something far worse than death awaited him. He wasn't sure how he knew that, but he knew.
A tsk he barely registered over the agony and the all-encompassing feeling of falling apart at the seams. “Weakened as you are, even with your soul being torn to shreds over and over again, you're still determined to exist, huh? Should've figured. Humans sure are stubborn. Alrighty. It was worth a shot. If replacing the human soul won't work, then how about…making her a part of you? A human absorbing a monster soul… Time to see if it can happen.”
He sensed the moment the entity stopped attacking his core and touched his chakra network, traveling through the pathways and passing through nodes as it flowed through his body. There was screaming, but the voice was muffled because all Tobirama felt was burning and pain and rage. His body…was splitting apart. Outside. Inside. His wounds were…tearing into his very soul. His chakra was flowing like a raging torrent, scraping each coil as it traveled through every limb, every organ, and every nerve. His body was melting. Crumbling to dust. It hurt.
He was dying, but…he was still here.
I'm still here…
Remember what you need to do…
Your duty…
The child…
He needed to protect the child. From them. From that beast. Beast? Beasts. Human? Humans.
He had…to live. For…the child. For…his brother. For…his clan.
For…her. For…land and leader. For…everyone's hopes and dreams.
He…won't…die.
She…refused…to die!
So stand…and fight!
“Just sit back and enjoy the show, buddy.”
Flowey eagerly watched as the adult human slowly stood up, having finally stopped his screaming and convulsions from the monster soul fusing with his chakra network—with his body. The kid was crying again, whimpering over Tobirama like he was afraid he wasn't gonna get up again. Puh-lease. He needed to relax. Flowey couldn't bring back monsterkind if this experiment didn't go well, so killing the human immediately was counterproductive. The enemy was basically on their doorstep now. Flowey could not wait to see what carnage would unfold the moment she woke up.
Footsteps approached. The vines hiding the entrance to the cave were moved. A flash of blue lit up in crimson eyes in response to the movement. Magic—chakra?—coalesced at the various wounds, cauterizing them just enough to keep bleeding minimal. Water droplets were pulled from the very air, shaping into a weapon Flowey was very familiar with. Before the ugly human's face even showed itself, the spear flew and pierced through the skull. And just like that, Tobirama grabbed the spear from the corpse before it even hit the ground and rushed out of the cave.
Screams echoed loudly outside. Many were cut short. Many others turned into gargling, incoherent noises before falling silent. Kagami, either very brave or very stupid, decided to venture outside. Flowey joined him and was delighted to see his efforts had borne fruit because the forest floor had turned into a bloodbath. Dead bodies strewn everywhere. Some humans were pinned to tree trunks by those water spears. And Tobirama? Completely coated in liquid red to the point where the color bled into the spear he held, smirking maliciously as he hunted down every single human that had chased after him and Kagami. Flowey was impressed. Who knew monster souls could harbor that much hate and determination after death?
Well, Undyne always was a gift that kept on giving. Ever the loyal soldier and ever a threat to humankind. She probably wasn't fully coherent yet, acting on the wisps of memory of her last moments. Her final stand against Chara, protecting a monster kid as if she had any hope of stopping Chara's genocide. She fought valiantly, even as her body melted from her sheer determination to defy death. But she could not change her fate nor anyone else's in the Underground. The way she was murdering these humans… It was revenge. For those who died by Chara's hands. For the home she could not protect. For the hopes and dreams that vanished as a result of her failure.
Oh. She turned that one into a pincushion. Flowey didn't know that many spear tips could fit inside a human body. You learn something new every day.
The forest was eerily silent now, the quiet only broken by the panting coming from the man whose body now housed the soul of the Spear of Justice. He certainly cut a terrifying figure in the night, the glow of the water spears highlighting the splatters of blood painting his hair, face, and armor. Kagami shivered as Tobirama—his weakened soul influenced by Undyne's vengeful one—slowly turned towards the boy. Flowey had to give the brat props for not bolting the moment those furious, bloodthirsty eyes landed on him. Was Tobirama actually going to kill the kid? Flowey hoped he would because it would mean Undyne had more control over the human body than Tobirama did, which was what Flowey was going for with that merge. Tobirama took several steps towards Kagami, tightly gripping the red-tinged water spear and raising it as if intending to throw it. Undyne never missed her mark. Even if Kagami ran, he'd be skewered before he took three steps.
Undyne didn't get the chance to throw it. Because someone leapt out of the trees and delivered a massive hammerblow into the back of Tobirama's head, knocking the human/monster hybrid out almost immediately. What an impressive sneak attack! This new person was not dressed in the same garb as the enemies that had been chasing Tobirama. No, the man looked quite similar to Kagami in terms of appearance and wear. Flowey dove into the ground, feeling like now was a good time to hide himself.
The black-haired individual with the deep-red eyes spat at Tobirama. “I knew not to trust that Senju scum and I was right. I can't believe I let myself think he was any different. Stay here and I'll bring him back, he said. I won't kill an Uchiha child, my ass. I'm glad I decided to trail him. Kagami, are you alright?”
“I-I-Izunaaaaaaaa!” Kagami cried as he ran towards the adult, practically launching himself at the one called Izuna. He clung to Izuna's legs like they were the only solid thing that made sense in the universe at that moment. “I-I w-was so scared!”
Izuma knelt down, pulling the boy into a gentle hug. “Shh. It's alright, Kagami. You're safe now. The White Demon can't harm you now.”
Kagami furiously shook his head. “N-No. Izuna, h-he didn't—it wasn't him. He wouldn't!”
Izuna blinked, confused. “Huh?”
“The White—no, Tobirama saved me,” Kagami explained. “He got hurt trying to protect me from those bad guys. He was trying to get me back to you. He really was! He didn't hurt me at all!”
“Kagami, I just saw him trying to kill you!”
“It wasn't him! Flowey did something to him and it turned him all stabby-stabby!”
Izuma gave him an incredulous look. “…What? Flowey?”
Kagami pouted. “The golden flower! There was a talking flower! It was just here! It said it would help him. Make him strong enough to get us both out of here alive. I-I told him to accept the offer. But it did something—put something in him and then he was screaming and I didn't know if he was gonna die and then he just stopped moving and got up and then there was water floating around and—”
“Kagami, I know it's been a rough night for you, but you don't need to make up insane stories to defend—”
“Don't kill him, Izuna!” Kagami resolutely said. “He saved me. He didn't want to kill me. He wanted to return me to you. That's the truth. If you hurt Tobirama, I won't forgive you! I'll hate you forever and ever!
“Kagami…” Izuna wilted. He looked at the fallen human and went back to the boy. He did this a few more times before sighing in defeat. “Fiiiiine. I won't kill him. It wouldn't be a satisfying victory if I killed my eternal rival like this, while he can't defend himself. And he did keep his word that he'd save you, I guess?”
Kagami smiled. “Thank you, Izuna.”
“Shut up, you brat. Don't think I won't try to get revenge the next time he and I meet. C'mon. Let's get you home.”
“Be sure to watch out for Flowey, Izuna! I think it's evil!”
“Don't worry. I won't step on any flowers along the way.”
Flowey snickered as Izuna left the area, carrying Kagami with him. He sprouted from the ground, looking at the unconscious human before him. He'd live thanks to Undyne forcibly closing the wounds with sheer will. Tonight's debacle was a promising start. Only time would tell whether Undyne would eclipse Tobirama's control or not. And if she did, there was hope for monsterkind to be reborn in human bodies.
If not…
Welp, there was still the option of becoming the God of Hyperdeath. Wouldn't that be a nice surprise for these humans; to have a new deity to bow down before and worship?