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Sukuna has always loved his brother. Well— unconventionally, really. With no parents around and a grandpa who only recently passed away, he had to take the mantle as caretaker eventually, and Sukuna gladly took the opportunity. He loved his brother.
He loved his kisses. He loved the sex. He loved spending every moment with him in the morning, in bed, under the streetlights and in the warm bath. It's nothing like how brothers should be, but it's their own world, so who gives a shit?
They trained in the same gym together. Muay thai, moved on from Jujutsu from their childhood when Wasuke was still alive. Sukuna liked the force. So did Yuuji. For awhile, Sukuna could pretend it was their own world in that gym too, they sparred and tumbled down together with broken noses and bleeding foreheads and patched each other up afterwards.
"You're not gonna get any stronger if you keep laughing like that, brat," Sukuna said as Yuuji laughed a nosebleed away with him. Sukuna thumbed the blood away from his nose and licked it.
"You're so gross!" Yuuji shoved at him. "Fine. Let's have at it again but after I plug my nose up with tissue."
"No headshots."
"What happened to not getting stronger?!" Yuuji asked. Sukuna slapped his ass, leading Yuji to yelp.
"Trust." He said, getting up.
Still, things have stirred up to try and endanger that world.
"YUUJIIIII-KUNNNNN!"
Exhibit A.
The grating sound of Satoru Gojo's coquettish enthusiasm came to the gym. Sukuna got up, watching as how the guy attacked his baby brother with a hug (a grab to the waist and a pull-in near the lips, to be exact) and Yuuji had the audacity to laugh while it happened.
"How's my boy doing?!" Gojo asked, swirling them around while Yuuji held onto him. "Oh! You're bleeding! Let me get my wet wipes—"
"That's really not necessary, Gojo-sensei, I'm—"
"No way! Come, give me your face," he said, not waiting for Yuuji to offer it— instead, he grabbed Yuuji by the chin and kept the blood from dripping into his face until Yuuji took to plugging it up to his nose.
"Still sparring with your brother, eh?" Gojo asked.
"Always have, Gojo-sensei," Yuuji said with a laugh. "What, you wanna have a go?"
Sukuna knows what flirting looks like. When you're gay, because Sukuna has in fact clocked that Gojo was also gay, every detail fucking matters. And Gojo doesn't seem to care that Yuuji was still a kid, (who cares if Sukuna was already an adult, this is HIS BROTHER, damn it!) he's going to take him if Sukuna doesn't do anything about it.
"Not this time, honey," HONEY?! "I'm gonna have to get ready for one of my students."
"Aw, not me?"
"You have your scary big brother, no?" Gojo said, ruffling Yuuji's hair. "It's okay. Let's spar once my session with my kid's over."
"Alright," Yuuji chuckled. He turned back to Sukuna. "Hey, Suku-nii, let's train more!"
Sukuna tried not to make a face. "Yeah. Get in!"
He knows the stupid fucking look Gojo gives when he sees Yuuji from behind. He has an ass on him. And Sukuna wants to make him wear looser pants so that never happens again.
"Gojo-sensei, wanna go for dinner with us?"
Sukuna choked on his protein shake. He shook his head vigorously as Yuuji pretended (pretended!) not to notice his physical refusal.
"Hm," Gojo thought.
Sukuna waved his hands frantically.
"Let me think," Gojo thought harder.
Sukuna nearly tried to scream as he shook his head.
"Su—"
"NO!" Sukuna snapped.
"Eh?" Gojo asked— but he still kept that stupid smile on his face. "Why not, Sukuna?"
"It was dinner for the both of us. Unless you wanna pay for yourself, Gojo?" Sukuna said as he calmed himself down. Yuuji hooked his arm with Sukuna's.
"Sukuna!" Yuuji said. "Well, I can pay for us, Gojo-sensei!"
"No." Sukuna replied, turning his head.
"Yes!" Yuuji replied, turning his head back.
"Aw, well, if your brother wants alone time with you, who am I to judge?" Gojo asked. "Next time, Yuuji-kun, maybe it can just be us two too!"
Yuuji kicked Sukuna at the back of his heel as Gojo walked off.
"Are you cheating on me?" Sukuna asked as they laid naked on the bed.
"What?" Yuuji asked, turning around. Sukuna lifted his head.
"Are. You. Cheating on me?" Sukuna replied.
"No." Yuuji said. "I don't think brothers can cheat on each other."
"Idiot. We're literally together." Sukuna said.
"Well…" Yuuji replied.
"What?" Sukuna scowled.
"I love you and all, but I kinda wanna get out there more." Yuuji said. "Aren't you tired of it just being us two?"
Sukuna paused.
"… Are you?"
Yuuji got up. "I love you. You know that."
"I do. I'm asking if you're tired of us being the way we are."
"I'm not. But… okay, maybe 'being tired' isn't the right way to phrase it. Sorry. I just… I want a thrill out of a new guy."
Sukuna was offended.
"Am I boring you?"
"No!" Yuuji jumped. "No, of course not. Just. Something new. Okay? I want someone new. We're still the way we are, I just… maybe I can have my own world too."
Sukuna's eye twitched.
"Besides, maybe this is good for us. Don't tell me you think I forgot about your thing with Megumi."
Sukuna sat up. "I didn't mean to—"
"I know," Yuuji replied. "But I'm letting you free for that. You can come back to him if you want to. As for me… well, I don't... I just wanna try this guy out. Okay?"
Sukuna swallowed. "I love only you."
Yuuji was quiet. "I love you too."
"Am I really not good enough for you anymore?" Sukuna asked.
Yuuji laid back down on bed, turning his back on him. "Ask yourself that."
They didn't train together this time. Gojo wanted to take Yuuji in for a spin, so now they're training in the ring while Sukuna was beating up some poor punching bag that did nothing to deserve the beatings it was getting right now.
"Nice job, Yuuji-kun!"
One punch. Gojo's a fucking yapper who can't shut up giving Yuuji praises.
"Really? I'm glad, Gojo-sensei!"
Two punches. Yuuji is talking back while flirting too— he can hear the tone he used to flirt with Sukuna; is nothing sacred anymore?!
Three punches. The punching bag is swinging violently. Sukuna crippled it with a kick as Gojo grabbed Yuuji by the ankle and pulled him down, only for Yuuji to strangle him with his thighs in miraculous timing.
"Ack!" Gojo said with a laugh, tapping out.
"That's not fair, Gojo-sensei!" Yuuji said.
"Sorry, just wanted to see what you'd do." Gojo said with a smirk. "Well, it sure seems cozy down here!"
"Sh-shut up!" Yuuji cried out, laughing while Gojo smothered his face on his thigh. He pushed him off him and Gojo fell to the space next to him.
"Guess we could have that dinner date tonight." Gojo said, turning to him, resting his cheek on his hand.
"Oh?" Yuuji asked. "What are we having tonight then?"
"Steak?"
Steak.
Sukuna's fist clenched.
He beat the punching bag until it nearly flung off the ceiling. Then he stayed quiet until their session ended. He ended up walking with Yuuji and Gojo towards the station, then as they started to talk, Gojo came with:
"Hope you don't mind me stealing your brother for the night, Sukuna." With that goddamn smile on his face.
"Actually, I do." Sukuna said, dropping his bag. Gojo stepped back— so did Yuuji.
"Sukuna?" Yuuji tried. Sukuna charged, bouncing off a wall and going to punch Gojo until he dodged.
"SUKUNA!" Just as Yuuji was about to get in the way, Gojo knocked him away and kicked away Sukuna's punch. He grabbed his wrist and pulled him forward, kneeing him in the stomach, while Sukuna pulled up and grabbed Gojo's head and shoved him to the floor.
"Hey! No shoving!" Gojo whined, twisting upwards and catching Sukuna's face with his heels. Sukuna tried to pull Gojo away, but Gojo kicked him away and pulled himself up. All the while, Yuuji was yelling at them to stop.
Sukuna launched forward again, making Gojo dodge and move away, blocking vehemently in reflex before grabbing both of Sukuna's arms and pulling him inwards to headbutt him.
"ENOUGH!"
Then two fists from one end stopped them both.
Yuuji landed a punch on both of their cheekbones and knocked them both down to the floor.
"Sukuna. Let me have this." Yuuji panted, seeing Sukuna look up at him. He snarled back, but Yuuji knows this face: he's going to be sad as hell when he gets home.
"Gojo-sensei, are you alright?" Yuuji asked.
"Yep! Thanks, Yuuji-kun, definitely needed that." Gojo smiled back, and Yuuji pulled them back up.
"Go home, Sukuna. I'll be back later." Yuuji said, not looking at him. Gojo slung his arm around Yuuji's shoulder and leaned against him as they walked off.
Sukuna picked up his bag and walked off.
Sukuna was reading a book when Yuuji came back home late.
"It's 2 am." Sukuna said.
"I got your text." Yuuji replied.
"Are you drunk?" Sukuna asked, turning around.
"No, don't worry about it." Yuuji said. His lips are puffy and his hair is messed up.
"Take a shower."
"Already did at Gojo's place."
Sukuna felt the tears sting his eyes.
"What were you doing at his place, I thought it was a date?" Sukuna turned around.
"Baby…"
"Don't sweet talk me." Sukuna's voice cracked as he glared at him.
"I'm calling you a baby." Yuuji said with a sigh. "Seriously."
"Seriously," Sukuna repeated. He put the book down and sat up. "You hate me."
"You're insecure."
"Why shouldn't I be?"
"That's what you called me when you did that with Megumi."
Sukuna widened his eyes. "Shut up about Megumi!"
Yuuji exhaled through his nostrils. "I'm sleeping on the couch."
"NO!" Sukuna snapped. Then he softened. "No. Stay with me."
Yuuji stared at him. He took his shirt off and slipped into bed with him.
"I still love you, you know." Yuuji said. "I can't leave you, but we're going to be together for a long time."
Sukuna wrapped his arm around Yuuji's body.
"If I could babytrap you, I would."
Yuuji frowned. "Don't even think about it."
"Too late." Sukuna snickered. Yuuji punched his shoulder. "Fine. How did the date go? Did he upset you?"
"You want that to happen, didn't you." Yuuji sighed. "No. It was worth the night."
Sukuna frowned. "Damn it. So you're going on more dates."
"Yes." Yuuji said. "Suku-nii, 100. Gojo-sensei, 101."
Sukuna sighed. Yuuji laid his head on his chest.
He was happy, right? That should be fine. Sukuna felt tired and decided to shut up about it. Maybe he's not allowed to voice how upset he is, but Yuuji will know that it's there. It just… does it really make sense to his baby brother?
Maybe it's fair. Maybe it's not. But he'll let Yuuji have this. Even if he'll complain all the way.
But Yuuji knows he'll stop complaining eventually.
He'll always come back to him after all.