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A Week of Sinful Stars

Summary:

Subaru from his IF routes visit Isekai Quartet, but through possessing the original Subaru, one at a time, while the original Subaru's soul watches in a spirit-like form, invisible to the others. This also happens to other characters from the IF routes, eg Emilia and Reinhard. The class has to deal with this for a week.

Notes:

If you read this chapter before 2026-08-07 then I'll just tell you that I honestly forgot to add Otto and Garfiel in, so I've added them in now. You don't exactly need to read the part I've changed, it's a small one and imo a bit rushed so sorry if it doesn't exactly fit.
I've watched only Re:Zero and TSOTTE, so research on the others will be pretty minimal. Also my memory sucks so things will most likely be pretty inaccurate, + I'm an anime only.
Mainly just trying to test out ao3 here... .
I will most likely release chapters like this, more of a "draft" version first, then a re-edited version. I'll be constantly editing with any feedback that you guys suggest if there is any!
Also I probably used the honorifics a bit inconsistently, sorry about that
Edit: bolded and italicized text was originally bugged, sorry if you had to read through the 10 million asterisks

(See the end of the work for more notes.)

Chapter 1: An Inferno of Memories

Chapter Text

“Ohh? What’s this?”

Roswaal sat at a desk, all alone in the teacher’s office, taking a break from marking his student’s assignments after a quite destructive school day. He had opened up his beloved Gospel in the meantime, humming a belated tune, curious at the sudden, drastic change of instructions stated by the book. The clown read through the newly written page, soaking in every word... Not that there were many words to deal with in the first place, only a single sentence scrawled onto the thin white page, awaiting its reader's obligation to follow.

“What an interestiiing new development,” He mused, not exactly disappointed nor appealed at the text, rubbing his chin. “This does not seem to bode well for the students, as weeell as myself…”

The Margrave calmly closed the tome, and placed it into his pocket, as he let a small grin fall upon his lips.

“I suppoose there’s nothing I can do about this… Fate has taken its turn." Roswaal sighed, shaking his head.

"Sooo I must assume... everything is going to be up to youuu again..."

"...dear Subaru?"


After school, a small trip to a park, and a restaurant for dinner, most of Emilia's camp stood at the front of Subaru’s house, ready to bid their knight farewell. It was soon to be nighttime, the distant sunset about to fade down the horizon leaving a starry night sky, with the reds, yellows and oranges morphing into deep purples and blues.

“Good night, Subaru!” Emilia waved, bowing slightly to the young man.

“See you tomorrow, Emilia-tan! Don’t forget your homework! Aaand, if you need some help, feel free to call—”

“Shut it, Barasu. Emilia-sama can clearly handle herself without you, out of all people,” Ram admonished, with her arms crossed, sending a sharp glare his way.

“Nee-sama, try to treat Subaru-kun more kindly,” Rem sighed with a teasing look on her face, despite knowing that her sister would not change. “But anyways, Subaru-kun, please get some rest. I will help Emilia-sama as she needs it.”

“Don’t forget me, too!” Puck suddenly appeared out of this air above Emilia’s shoulder, raising a paw. “Though Rem is right, you seem to be quite tired. Your gate isn’t exactly filled with mana yet, especially since you let out quite the barrage of spells earlier with Betty.”

“Bubby is right, I suppose…” Beatrice huffed just in front of Subaru, a little bitter that she wasn’t able to point out the fact to her contractor first. “Betty’s contractor should be filled with mana tomorrow, so Betty can fully support him, in fact.”

“Yeah, yeah!” Subaru said, resigning. “I get it, you’re all worried. But I’ll be fine! Just a little rest and I’ll be back up, ready to go tomorrow.”

Ram raised an eyebrow, as pessimistic as ever, and even Puck looked a bit concerned at his enthusiasm.

“Subaru, I will be fine,”—Emilia let out a small giggle—”just get some sleep, and I will see you in the morning.

“Of course, Emilia-tan!” He flicked a thumbs-up at the women and spirits, ready to plop onto his bed. “Again, good night!” Subaru entered his house, looking to close the door behind him, and watched Emilia, Rem and Beatrice waving goodbye through the door’s windows. The door locked with a click, and Subaru took of his shoes, walked past the main entryway, and saw Otto and Garfiel, who had not decided to come along on their stroll earlier, in the living room. They seemed to be quite audibly fighting about something. Before Subaru could start panicking, he came closer and found that the two friends were playing a fighting video game connected to the TV, to which Garfiel seemed to be struggling with. Snacks littered the table before them, along with some empty cans and crumbs.

"Aarrgh!" Garfiel fidgeted with his controller, frustrated. "This thing ain't workin' properly! It's not working when I press these buttons!"

"Have patience, Garfiel! You're gonna break the controller!" Otto panicked, trying to calm the boy down. The two sat on a couch facing the TV, and it seemed that Otto was winning whatever game they were playing, the one HP bar on the screen clearly near death. 

"Hey!" Subaru greeted his two friends, sidling up behind the couch. "I'm gonna head off to sleep. Make sure you don't sleep too late..." He looked pointedly at Garfiel.

"Aye Cap'n! Of course my amazin' self wouldn't do that!" Garfiel waved, flashing his sharp teeth with a grin, almost dropping his controller. 

"All right, Natsuki-san," Otto sighed, knowing that the responsibility fell to him. "How were your travels, though?"

"Ah, it was good, the restaurant we went to had some delicious food," Subaru walked to the stairway close by where he could still see the living room, and climbed up a couple of steps. "You should come along next time,"

"That's good! All right, good night!" Otto waved agreeably, giving Subaru a faint smile.

"G'Night Cap'n!" Garfiel said right after, and went right back to pressing some buttons. 

"Night!" Subaru said goodbye, and continued up the stairs, holding the wooden railing as he walked up the carpet.

He then went to the bathroom to wash up, getting rid of the many dirt stains on his arms from the ruckus of the previous class activities that had gained him quite the curious glances at the restaurant he had gone to, and then got a change of clothes. After cleaning himself up, he walked towards his bedroom, ready to settle down and rest. He opened the door, yawning.

I guess they were right… I am pretty tired.

Subaru’s room was dimly lit with the curtains closed, and overall pretty drab with a lack of colour. Generic pieces of furniture could be found in the cramped room, a small double-sized bed, a desk with a gaming PC, and one big dresser filled with many plain shirts and pants. The anime figures and posters that had adorned Subaru’s room back on his Earth were nowhere to be seen, the only real personal belongings being some photos with Emilia and the others, some even with his fellow classmates, allowing fond memories to resurface if just for a moment. 

Wow, now that I think about it... I should probably liven this place up, though at the same time I don’t spend much time here. (Haha, I’m definitely not a NEET anymore!) …But again, I am sort of broke. Maybe I should get back to doing that part-time job at the Karaoke place, though the experience was… sort of interesting… Subaru lamented, running his hand through his disheveled hair. Having a whole house to himself when he had first been isekai'ed to this world was a thought that had never occurred to him before, even though he had lived in a mansion where sometimes it felt like the whole place was to himself due to its hugeness. He missed having company from the maidens of the mansion, though Ram would surely decline if he tried to offer for herself and the others, but at least Otto and Garfiel were here at the present... Though Subaru was a bit unsure as to how they even arrived. In contrast to the moments filled with silence when he lived alone, the faint sounds of his friends could still be heard through the somewhat thin walls, fussing over their videogame. 

Subaru let out a deep breath, and faceplanted on his bed, ready to fall asleep. He then sat himself up properly after taking a moment to just lie down, and pulled the covers over, letting his thoughts lullaby him to rest. Since coming to this new school world, he was able to avoid past nightmares and struggle sleeping, yet he still couldn't quite plop onto bed and sleep like a log. He tossed and turned, trying to relax his mind. 

Class today was pretty fun, getting to test out magic from other worlds, all of those cool magic systems in play. I don’t know why, but the whole time Roswaal was giving me funny looks. But that clown always looks funny, sooo… Anyways, the homework was pretty easy, so I could finish at school. I hope Emilia will have an easy time with it, she didn’t have much time to work…

As Subaru drifted off to sleep, a sudden headache anchored him back to full consciousness.

“What the hell—” A pulsating wave of pain washed through his mind, causing him to curl up into a blanket ball. It felt like something was trying to take control, to take over his body, just like how Petelgeuse had tried to possess him before, leading to an unthinkable present. No… The struggle was worse. Much worse. This new force was unstoppable, battering at his brain, leaving almost no openings to form coherent thoughts, winning the battle for control. Garfiel and Otto's jabbering faded into the background, Subaru's ears ringing from the strain. 

Strange, unknown memories flooded into Subaru’s brain — reforging, remaking — no, renewing the person that Natsuki Subaru was, into something that was not. Every moment, every emotion, every sense of this other being was poured forcefully into the brain of the young man lying painfully on the bed, taking over his complete sense of self, fundamentally becoming the owner of the memories themselves.

Wait… this is… me?

Subaru barely managed a thought, the overload of senses and memories not faltering even a bit. His body automatically braced himself out of fear, hugging himself closer, yet the effort was ineffective, the impact solely psychological. 

No. It couldn’t be. Subaru let out shaky breaths, trying to survive the pain plaguing his mind. He clearly could not comprehend the fact that…

These memories… Were his?

Subaru stood in front of the three stooges, eyes blazing with fury and disgust. After taunting them, he swiftly and mercilessly took all three down, leaving three mauled, bloody corpses on the ground. He went into the main streets of Lugunica at the sound of a silver-haired half-elf’s voice, eyes crazed, bathing in glee at every syllable pronounced by the young woman.

No… No. That’s not how—

Subaru stood in the Loot House, cautiously stepping over the rubble caused by the Sword Saint.

He offered a hand to an injured woman with black, braided hair, slowly recovering, though not steadily, from her severe injuries. He took her to a young woman with blue hair, who healed the Bowel Hunter, forming a sort of sense of respect for each other.

Elsa…?

Subaru looked upon a strange group of people, all varied in appearances, yet one thing that unified the group… Was their sense of insanity. Subaru proudly accepted their help, using it as a chance to get closer to “her”.

Subaru was then seen in a secret enclosure, joyfully celebrating at the broadcast of his beloved’s name, while bearing a Witch Cult outfit. The archbishop of Sloth, green skinned, bare corpse of a man, stood beside him, revealing the Witch Cult’s plans in a manic matter. Subaru frowned, realizing that hanging with the Witch Cult may not be so beneficial for his love, after all.

Soon enough, Subaru stood over the corpse of his former ally, the slothful archbishop, though the archbishop’s actions may have seemed diligent to many. The blue-haired girl that had patched up the Bowel Hunter stood by Subaru, watching on at the murderous act.

Subaru listens to the news with glee, as Emilia is recognized for defeating the Archbishop of Sloth, with the assistance of her benefactor. He then goes to a cell, where the once-great healer, Blue, could be found, looking quite pathetic without his candidate who had lost everything thanks to the White Whale. Subaru looks him in the eye, promising to use him the best he can.

A white-haired man screeches at Subaru, as flames burn all around a now ramshackle mansion, preventing the once-invincible man’s safe escape. The vampire assassin swiftly cuts off all the man’s limbs, skewers him, and throws the man’s limbless torso into a fire, where the two maniacs watch him burn, his pitiful screams echoing into the night, then eventually dying off.

Subaru stands before with his newly reformed healer, Blue, before a young man with purple hair, known as the Knight Impeccable. The knight, near death, rather than begging for mercy, just looks upon the two, astonished as his old friend puts him to rest. A young, grim, grey-haired man arrives for the cleanup, looking quite unwilling to do so, even with Subaru’s expressed gratitude.

…Otto… Julius… No….!

The Capital had been set ablaze, infernos everywhere, consuming everything in their path. Not a single living being could be seen through the flickering flames and ashes, aside from Subaru, dressed in a Witch Cult cloak, gently setting the blue-haired girl seen with him previously to rest.

Subaru looks up, taking in all that it took to get to this point. All of his sacrifices, the whole nation of Lugunica, all for the sake of defeating him.

Reinhard Van Astrea.

Hate flowed through every essence of Subaru’s veins, and getting rid of the Sword Saint’s sole duty of the kingdom… The sense of satisfaction was immeasurable.

Subaru left the Sword Saint to his own misery, and alas… his final goal… there she was.

Emilia. His one guiding light that may have just been an illusion, but no. She was there, and she was about to kill him.

But it was fine. He was content. He was satisfied, leaving Emilia with the throne, and tears that no one could explain. Death took him, the familiar shadows clouding over his vision, welcoming him into an endless reality of shadows.


The flood of memories was over.

It was over.

An abrupt wave to the tumultuous wave of vivid emotions, visions and experiences, a circuit that had been cut short. It was over, and Subaru was back to himself… But he wasn’t in his room any longer, now resting in a garden of shadows, an unending expansion of darkness, only left to one single being that pulsated an emotion so strong, it could make almost anyone feel better.

“I’m… back? Why am I…” Subaru looked at his surroundings, confused, because this meant he surely must have died, as that was how the visions ended. “But… I’m myself. That— that wasn’t me… Why am I here?”

“I love you.”

Satella approached Subaru, and wrapped him into her shadowy embrace, then sent a calm flow of love over his heart, reducing the pounding headache and the immense stress the memories had placed upon him. Her gentle touch caressed Subaru, her warmth attempting to bring a sense of peace to the young man.

“I love you.”

And right then and there, Subaru burst into tears, unable to contain the emotions that the memories of the other “him” had caused.

Subaru held fast to Satella, each tear that fell out containing a lifetime of fear, disgust, hatred and sorrow. Going through all of those atrocities he had committed by his own hands, every unjust immoral thing he had done— to his friends, even his foes, and even to his allies who might not have been the most morally right, but did not deserve such as fate as that.

As Satella’s embrace began to let Subaru regain his bearings, Subaru began to deduce that this had to be some sort of other reality, another timeline where Reinhard did not come to help him at the start. It reminded him of those horrible “unthinkable presents” he had witnessed in the second Sanctuary trial… but this was too real, too vivid compared to the visions from Sanctuary.

But the worst part was, the one thing that Subaru did not want to think about was... that he very well could have turned out like...

that.

He understood. Understood that no matter what that “Subaru” had done, he could not be saved, without Reinhard or another person rushing to help. He was only an immortal puppet that only the fate of death could toy with, taking his sanity away, bit by bit. He was only able to see the option of killing the three bandits, and that led him to an ultimately darker path, long gone in morality. He was truly helpless, with no one to guide or support him, a pathetic human being only trying his best to live. Emilia was the only string of hope he could hold on to, and said string eventually turned into a barbed wire of obsession.

If only that version of him had tried harder to ask for help, perhaps even begging, sacrificing his pride to do so, then maybe…

And, not to mention, it was all for a debt that did not even need to be repaid.

It was hard to believe he would really go that far... Eighty-eight deaths... That was even more than he had experienced throughout the whole of his adventures. Why didn’t he give up? Move on with life? Why was he so damn stubborn…?

“But… I guess that’s what gotten me to this point,” Subaru mumbled. The three deaths that it had taken to even get to Roswaal’s mansion were extremely painful, but he had kept going despite that, even after dying many more times afterwards.

“Man, I was so lucky… That Reinhard came…” A pulse of sudden gratefulness washed over Subaru, yet he uncharacteristically flinched at the name even though he said it himself, the vivid memory of that other him still reminding himself of the hate that he had for the Sword Saint, the sensation having come in full blast.

“I love you. I love you. I love you. I love you. I love you. I love you. I love you. I love you. I love you. I love you. I love you. I love you. I love you. I love you. I love you. I love you. I love you. I love you. I love you. I love you. I love you.“

“…” Subaru finally decided to stop panicking in frustration and sadness, and knew that his priority should be getting to the root of the problem. Why in the world was this happening? The situation was clearly unusual… Did he really die in his room? Or was he just summoned here? Who or what could have possibly sent these visions to him? The nature of this “school world" was pretty peaceful, and surely, if there was a big threat someone like Reinhard, or Ainz could sense it. 

…Well, knowing his luck, things were probably going to get worse.

Plus... if this was happening to him... did this mean that his friends were experiencing this too? Had Otto and Garfiel heard his cries of pain? But since they didn't seem to come...

He shuddered at the thought.

Subaru loosened his squeeze on Satella, the tension of the moments before fading away. Satella followed suit, stepping back, clasping her hands together, returning his determined stare.

“Are you gonna let me back yet? I mean, I have many questions and all, but… is this where I’m supposed to deal with the problem? If you’re the one that sent those visions… It would be pretty helpful for you to say something that isn’t ‘I love you’ for once. Hey, your words at the Witches’ Tea Party were… pretty helpful.”

For some reason, Satella paused her flow of “I love yous”. She glanced up at Subaru, and, a pitiful look could faintly be seen from her dark veil, amethyst eyes filled with sorrow.

“…?” Subaru’s eyes widened.

“I love you,” She repeated. But for some reason, it sounded more like an affirmation.

“Yeah. I know that. I’ve known that for a while.” Subaru sighed in resignation. He looked down to the side, wearing a faint expression of sadness.

“I am sorry.”

Subaru's head snapped right back to Satella.

“What?—”

As those new, never-spoken words came out of the Witch’s mouth, Subaru’s soul was suddenly sent back to his world — however, not exactly in the way it was before…

Notes:

You can give feedback if you want, especially for characterization, pacing, or grammar, just please be lighthearted :') This is my first fic and I haven't written any stories in a LONG time, so I apologize if my writing is absolutely trash.
I actually might include some drawings since I'm not bad at it, if this goes well enough.
I'll try to go for monthly chapter releases, just don't get your hopes up. My motivation levels are really inconsistent, and I've never written a full fic before.
I'm honestly going to just get rid of Eminence in Shadow characters and perhaps most of Class 1 because I am not dealing with writing that many characters lol... I know that the timeline doesn't necessarily line up with some of the events that have happened. I'd like to say this takes place at the start of S3.