Omega sukuna pretending to be an alpha so he can steal omega Yuji away from his family. Yuji had been taken in by this family after his grandfather died because they wanted an omega they could use as a bargaining chip, which is why sukuna could never be together with Yuji normally, their families would never accept a omega-omega relationship when there’s so many influential alphas vying for Yuji’s hand.

Their families were in the same social circles but they never met officially; sukuna was aware of Yuji and thought for years his aggression and intense feelings towards Yuji were a mix of hatred and jealousy, it wasn’t until uraume pointed out sukuna was actually upset that he couldn’t fold Yuji in half beneath him and drown Yuji in his slick to mark his territory.

He got so possessive over Yuji being his that sukuna lost it when alphas started approaching Yuji with intentions, and he got caught sabotaging the pairs and mistaken for an alpha due to his looks and aggressive nature towards other alphas over an omega. Sukuna would hear about an alpha visiting Yuji and go beat up the alpha for daring to look at his mate without sukuna’s permission or straight up ruin the family as punishment.

Sukuna spends all of his heats alone, wishing he had Yuji, because his hatred for alphas so is deep he ends up killing or maiming any alpha that crosses his path when he’s in heat. When he finally has Yuji with him for a heat, he’s insatiable and clingy, Yuji can’t go anywhere without sukuna and sukuna alternates between wanting to feel Yuji deep in his womb and wanting to crawl into Yuji’s womb to mark his territory.

Sukuna non conning step mom Yuji In her sleep; his mommy issues coming up full swing with how Yuji tries to dote on kuna and he can’t hold back.

His dad, ryomen knows what sukuna does to Yuji at night, maybe there’s a reason why she’s such a heavy sleeper. Maybe he’s even got a hidden camera with audio set up so he can watch from his office, I mean he did marry Yuji for her mothering personality winning him over.

Yuji and ryomen have loads of sex and ryomen is always pushing for it when sukuna is around, much to yuji’s embarrassment because she doesn’t want her step son catching them.

She doesn’t know that both son and father like the idea of fucking her as sloppy seconds.

The master suite bathroom is double bugged with cameras, one for the son and one for the father, so they both can enjoy watching her clean out her pussy after ryomen fucks her.

Kuna doesn’t wear any condoms when he has the time to slurp out the cum him left in Yuji.

Kuna gets extra moody when Yuji tries to prod him about crushes and potential partners; he only has room in his heart for his step mom, but he doesn’t have the emotional intelligence to seduce her properly (he gets tongued tied when he even thinks about it).

Yuji is on birth control because ryomen doesn’t like the idea of sharing her tits with another kid, and kinda humiliates Yuji with the idea of her getting horny if their baby sucks on her tits because of how ryomen treats them.

Omega Yuji using his own slick as lube for when he finger preps his alphas, sukuna and satoru. Sukuna is facedown, nearly smothering himself with the pillow, because he’s super shy and embarrassed about how much his dick is leaking, and satoru is covering his own face with his hands because of the same thing; both of their knots have started swelling prematurely the moment Yuji stuck his fingers in them. They’re trying to prove they’re not like other alphas, but they’re both acting like virgins tops who are bottoming for the first time; they want Yuji to say yes to their betrothal offers and the condition was him getting the opportunity to fuck them.

Yuji is cooing and purring because he’s got two alphas leaking all over themselves in his nest, and he’s going to stick his dick in both of them.

What no one knows is the reason why itadori omegas want an alpha to submit to them sexually, at least once, because it hardwires the alpha brain to associate pleasure and attention to the omega fucking them, rather than aggression/territorial instincts from bottoming, once the omega gets them to knot and cum from penetration because the omega is giving out satisfied and happy pheromones, the alpha brain is like wait a minute they like when I do this so I’ll win if the omega does this to me. Even if the alpha only allows it once, they will be instinctively seeking out that specific jolt of pheromones from a specific omega (wives tale is the alpha is too embarrassed and shy to leave/cheat on the omega that fucked them out of fear of retaliation or such and such).

The brother threesome picture gave me thoughts.

Oldest sibling ryo got tired of middle sibling kuna being a huge brat and roped youngest sibling Yuji into punishing him.

Ryo gagging kuna with his fingers, basically throat fucking him so he can’t distract Yuji with his whining and complaining (swearing and cussing them both out).

Yuji is a horny teen, trusts his big brother without question, and craves kuna’s attention, so when ryo told him to fuck kuna, Yuji agreed to it.

Yuji feels absolute love for his brothers and didn’t want to hurt kuna (aka make him resent getting fucked / it’s not rape If he’s gentle), so he prepped kuna nice and slow. He even ate him out so it would be nice and special for him.

Yuji still has a big dick tho, they all do, and even tho ryo is telling him to shove it in, yuji doesn’t want kuna to hate it, so the first thrust so slow, gentle and absolutely dripping with lube.

In the mean time ryo has been taunting kuna, calling him a slutty bitch and whispering how well Yuji behaves for him and how kuna will never be strong like him (very im the top bitch and you’re just a fake loser kind of sibling insult). He even shows off how well Yuji listens to him by telling Yuji to open his mouth so he can spit in it.

This is Yuji’s first time (kuna’s first time bottoming) so it doesn’t take long for him to cum, so he’s just boneless on top of kuna, leaving him plugged with his softening dick.

Kuna didn’t come but he’s close, he hates that he loves being the center of attention, pressed in the middle of his two siblings. He hates how Yuji came in him, still has his dick in him but hasn’t done anything to make him cum.

Ryo then proceeds to tell Yuji to frot against kuna while ryo uses his spit and Yuji’s cum to prep Yuji to get fucked now.

Kuna is flushing, it’s from humiliation at how much he likes yuji’s dick rubbing against his, how he can feel how hard ryo is thrusting into Yuji, and just how hard he his from it all.

He forces Yuji to kiss him, and ryo feeling left out, forces his fingers between their mouths so they’re making out with each other and his fingers.

Kuna comes from Yuji rubbing his dick raw on his, ryo fills Yuji with cum, and after he pulls out, takes a picture of both his baby brothers leaking cum.

Kuna passes out from overstimulation and Yuji is boneless on top of him while ryo is just petting Yuji like a dog and telling him see, kuna needs a heavy hand to be good boy like you.

Ryo is the oldest, clan heir and has been groomed to be perfect. Kuna is the middle child who got spoiled and left off easy since ryo was always there to be the responsible one. Kuna started changing when yuji was born, because yuji was the favourite child of their parents, so they tolerated kuna’s attitude less. But yuji loved his brothers equally, trailed after ryo and kuna like a needy puppy, kuna made him cry when kuna didn’t want to play with him. Of which ryo benefited from because yuji would run to him crying, his crying face is the cutest.

Ryo has been grooming them both to be codependent on him and each other, he absolutely hates everyone else, views the rest of the world as beneath him, and if he has to be clan head who has to deal with garbage people for the rest of his life, he might as well have something to call his own.

Kuna has issues because his whole life has been, why can’t you be perfect like ryo (he does get perfect marks, masters any sport or hobby instant so no one but his older brother can compare), and when Yuji came around, it drove him mad when Yuji wouldn’t look up to just him, he wanted Yuji’s full attention and love.

Yuji just wants love and attention from both his brothers. His fav was when they would cuddle together and have sleepovers when they were young but now all kuna wants to do is fight and bully him and ryo is super busy with heir stuff.

Everything comes to a head when kuna beat up another clan heir for saying shit about in to his face and ryo had to cover it up, and Yuji came home from school to their shouting match where kuna was seconds from attacking ryo.

Afterwards, ryo puts kuna in a cock cage for a week as further punishment, and only lets him out when he begs sweetly, and as incentive, gets Yuji to wash and handle his dick while ryo watches. At the end of that, he fucks kuna while kuna fucks Yuji because he knows kuna likes being sandwiched between them and he likes when Yuji is whining because of him instead of ryo.

Yuji and ryo have been fucking around for while; no penetration other than his fingers so it’s mostly yuji being taught how to suck his dick, and ryo fingering him, as he didn’t want kuna to left out (he knew it would make kuna absolutely worse to handle if he found out ryo and yuji were fucking behind his back), but he wanted Yuji to associate pleasure we his siblings and no one else. High school was full of whores who could lead his baby brother astray as what happened with kuna.

It’s not uncommon later on, for ryo to come home after late clan meetings to find his brothers passed out and naked in his bed, both of their holes dripping cum and ready for him to slide into either of them, while they’re clinging onto each other.

Future musing: yuji is the first to get a marriage proposal since ryo keeps stalling the offers for his own hand by ignoring the hints people keep giving him about their available family members, and no one wants to marry kuna because he’s a terrible person, which has both of his brothers angry and upset, that’s their baby brother.

Newly presented Alpha Yuji being shown how to knot by alpha kuna as kuna picks an omega that he can kill after Yuji fucks them. Kuna is repulsed by omegas and was happy Yuji presented as an alpha which doesn’t mean they’re not mates, it just makes it harder to be around each other without omega pheromones tempering their aggression in a rut. You can’t bitch alphas who have cursed energy in this au, and Yuji and kuna have been in an arranged marriage and mating since they were born, and everyone including Yuji was upset that him presenting as an alpha would call it off, but sukuna was like no wait babe I got this.

Yuji or kuna uses the omega, knotting them over and over until their rut is done and then the other rips their throat out with their teeth, because rut instincts to breed keep the possessive-territorial instincts at bay so once the rut clears they’re incredibly how fucking dare you touch my mate bloodthirsty. Also since they’re mates, their ruts sync up, so they share the omega, using them as a glorified sex toy, their instincts wanting to breed the omega like they’re competing for the womb.

Outside of rut, they have no issue with switching/bottoming.