Work Text:
Katsuki and Eijirou are in a loving AlphaAlpha marriage and Eijirou doesn’t regret a thing.
But, he can’t lie about the insecurities he feels about their unique relationship. It was looked down upon in society for same second genders to marry. Something about how it wasn’t natural, wasn’t part of their biology to be with the same presentation. They face discrimination and dirty looks whenever someone finds out they’re both alphas. Society doesn’t believe that they will work out. They think it is unhealthy for them to deprive themselves of their natural instincts to be with a submissive omega. If two omegas were together they faced even more discrimination and threats out in public.
Eijirou tries to talk to Katsuki about considering a transition. He’s thought about it for awhile. Transitioning into an omega so that they could be true mates and could produce a child. He wants to be able to satisfy Katsuki’s alpha instincts during rut and hates seeing him in pain while he locks him up in their room and hears him growl and scratch at the door, begging for an omega to fuck.
But Katsuki just shuts him down everytime. He tells him that he’s being dumb and he shouldn’t let others opinions get to him. That he loves him just the way he is. And Eijirou loves him too but he craves to be closer to him. To be connected through a mate mark and to feel his partner’s presence wherever he goes.
When he makes an appointment to see a second gender therapist that excels in A/A and O/O marriages, he can’t help but feel excited. He doesn’t tell Katsuki, knows he has to keep it a secret from him or else he’d become livid.
The therapist is nice and gentle and listens to all of Eijirou’s concerns. It is easy to get comfortable with him and spill out all of his fears and worries. He tells him he wishes he was an omega so he doesn’t have to go through all this. Would love to sacrifice his alpha status so he can please his husband. He says he wants to do the transition and the therapist nods in agreement.
He tells Eijirou he should bring his husband here to discuss all this before taking action. But Eijirou shuts him down, telling him Katsuki would never go along with it, that he’d be so angry with him for even coming to a therapist for this reason. He needs to do it in secret, needs to tempt his lover to knot and mark him into becoming an omega.
So the therapist explains the bitching process. Explains the different ways to do it and that if he convinced his husband he could change gradually, could drink his alpha come daily and it would change him without any discomfort. But Eijirou refuses. He knows his husband won’t agree. He sees it needs to be the quick process. The process where the alpha who is being turned needs to get fucked, knotted, and marked by an alpha in rut in order for the omega process to activate.
So the therapist teaches him how to use his fingers to pleasure himself. Tells him to use a lot of lube and to relax and exhale slowly as he slides his fingers into his hole. Shows him where his prostate is located and how to get pleasure from it. He tells him to jack off while he fucks himself on his fingers, to clench his fist around his knot to associate the two pleasures together as he comes.
At first, Eijirou is flustered and embarrassed. The feeling of the doctor watching him as his fingers, covered in lube, slide into him makes him blush all over. It feels weird and uncomfortable to have something inside him. The foreign feeling makes him tense up and in the back of his mind his alpha is telling him this is wrong. But he tries his best to ignore it and focuses on his cock. He imagines Katsuki’s mouth around him, sucking him down as he slides his hand over his member. He thinks of his husband using their flesh light on him as he kisses and nips at his neck, whispering dirty things into his ear to help him reach climax.
He fingers himself into an orgasm with the thought of his husband.
After the first session, his therapist gives him a few dildos that range in size and he’s so fucking embarrassed but he takes them home, hiding them under spare clothes in his gym duffel bag.
When Katsuki’s at work, he rides the smallest dildo in the bathroom. Jacking off once he fits the entire thing inside him. It’s uncomfortable and and makes his ass ache but he’s able to come quicker than at the therapist office.
He gets a lot of alone time because they work opposite schedules, so he finds himself stuffing his hole full of fake cock quite often. Makes sure to jack off every time he sits on one. Associate both pleasures, his therapist told him.
Whenever Katsuki gets home, they end up making out and rubbing their cocks against each other. It feels so good to have his husband against him, his scent all around him. But he can’t help but crave fingers inside him. He doesn’t tell Katsuki, but he’s having a hard time coming with just his dick being rubbed. He wants something more, needs fingers inside of him.
When he finally gets the guts to take the biggest dildo, he goes back to his therapist and brags. He's ecstatic. But his therapist only chuckles and says he still has one more to go.
When Kiri's given the new dildo, he stares at it nervously. A much thicker dildo with an even thicker knot at the base. He doesn’t know if how he’ll fit the knot in his ass but he’s going to try anyway.
He makes sure to hide the knotted dildo in a safe spot when he gets home. He tells his lover he was busy at a work meeting every time he goes to see the therapist. He doesn’t want his husband to find out. He’d be furious to know that he’s going behind his back trying to plan this transition without him. But Eijirou wants it, and he knows Katsuki would like it, would probably love it. Plus, they wouldn’t have to suffer during their ruts anymore, clawing desperately at the door for something to fuck while the other waits outside and hopes the rut cycle ends fast.
When he is home alone the knotted dildo is almost impossible to fit in his ass. He cries and groans the farther it sinks into him but he can't seem to pop the knot past his tight rim. He gets it only 1/3 of the way in and ends up coming without touching his cock. It shocks him, to see his dick jerk as come spurts out of it and his knot forms with nothing around it.
Every day when Katsuki is away, he tries the knot. He fingers himself with a generous amount of lube and slathers the dildo with it as well. And every day he prematurely comes before the knot is fully seated inside him. He’s only ever made it as far as a third of the knot.
Katsuki's rut is coming soon and Kiri gets frustrated and goes back to the therapist.
The therapist gently smiles at him and tries something new this time.
He lays Eijirou on the couch and puts lubed, gloved fingers into him. The therapist barely has a scent, covered up with scent blockers, so it helps when he tell him to imagine him as his husband. He works him open and whispers dirty phrases into his ear and Eijirou feels like he's cheating but he's not because this is for medical purposes, right? He comes before the dildo is even inside him, then comes again when the knot fully seats into his tight hole.
He goes home feeling satiated and happy. Thinks that maybe now he should tell Katsuki what he's been up to now. So they can both agree that this is what they want and he won't end up hurting him.
But when he opens the door to his home the stench of an angry alpha infiltrates the air with an underlying scent of pre rut. Eijirou is immediately concerned and rushes into their bedroom to find Katsuki. But when Katsuki turns to him, ember eyes glaring daggers at him, Eijirou gulps.
"Is everything okay? " he asks, placing a hand on the alpha's shoulder. Katsuki shoves it off and growls threateningly.
"What do you think, you slut?" he spits the word out with extra venom.
" What the hell, Katsuki?"
"I thought you were telling the truth about 'work meetings' until I fucking ran into dunce face." Katsuki says lowly, as he advances on Eijirou, backing him against a wall. "But he said there hasn't been any work meetings in months." And Katsuki's voice drops threateningly low. "So, Eijirou. Tell me who the fucker is so I can kill him after I teach you a fucking lesson. " he snarls.
"No, no its not like that, I swear! " Eijirou sputters, hands raised defensively. “Let me explain!”
And Eijirou spends the next two hours explaining everything that has happened so far. He tells him about the therapy sessions, the dildos, the grooming to come without touching himself. All of it. His husband seems to calm down a bit. Jealousy spiking at the fact that another person was touching his lover but Eijirou quickly stampers it out, explaining it was all professional.
Relaxing a bit, Eijirou can tell Katsuki does the same, his furious scent calming down. Still the smell of the underlying anger and rut stirs beneath his neutral burnt cedar scent.
"Show me proof." he orders, his ember eyes boring into Eijirou’s ruby ones.
They end up on the bed with Eijirou on his knees, a quivering mess as the knotted dildo sinks halfway into him. His arms are shaking as he holds himself up, rocking his hips to slide the dildo into him a little further. He’s breathless and whining as he looks between his legs, watching as the large knot at the base bumps against his entrance.
Katsuki is growling behind him, an erection tenting in his pants as he watches Eijirou squirm on the thick knot, trying his best to force it in. The red headed alpha can smell Katsuki's arousal and his rut scent resurfacing as he feels the knot sink into him until he’s fully seated himself on the fake knot.
He comes immediately from it, his cock jerking and spurting from the knot stretching him open and pressing against his prostate. Eijirou chokes out a sob as he rides his orgasm out, body shuddering with the intensity of it.
And Katsuki, well, Katsuki rumbles in approval at the sight and sinks deeper into his rut.
"Enough." he says but it comes out animalistic and gravely as he advances on Eijirou. Pushing the alpha to lay face down on the bed, he cards his fingers through the red locks gently before tugging at it, a sharp growl leaving Eijirou’s mouth at the sting.
Clenching his jaw shut, Katsuki growls threateningly in his throat. Baring his teeth at the other alpha, a warning to submit. He shoves Eijirou’s face into the pillow beneath him and positions himself behind the red head. He tries his best to remain clear headed but he can feel his rut sinking in. Feels the animalistic need to take and claim and fuck Eijirou into submission.
As he slides the knot out of the alpha's hole, he groans, watching as it greedily clenches down on it before the rim finally gives in and lets the rest of the dildo slide out with a loud squelch.
He watches as Eijirou's ass clenches around nothing and Katsuki loses his willpower. "Gunna knot you." he groans out as he sinks two of his fingers into Eijirou's hole. "Fill you up with my cum. Fuckin' turn you into an omega bitch, like you've always wanted." He rasps out, positioning himself behind Eijirou as he pushes his pants down, his hard cock bobbing out of its confines. “Such a fucking slut, coming just from being filled by a fake knot.”
Katsuki taps the head of his cock against the alpha’s entrance, watching as the alpha rocks his hips back to meet his. “I’m going to give you a real one.” he promises, voice husky and deep.
Eijirou rasps, “fucking do it already” snarling at the blond alpha. He can feel his fight response starting to kick in, the alpha side of him telling him this is wrong, and he tries his best to keep himself still. “Will you hurry u-!”
Katsuki shuts Eijirou up quickly as he sinks his cock into him in one smooth thrust. He slides all the way in until he bottoms out, pushing his hips snug against Eijirou’s ass. His hands are at his husband’s hips, digging in with his fingers which he knows will leave bruises.
Arching his back, Eijirou half growls half moans at the feeling of being stretched and filled. The sensation is so different, he feels how hot Katsuki’s cock is inside him, how it fills him up nice and full.
Eijirou whimpers as Katsuki starts to move, sliding his cock almost all the way out before plunging back. He does this several times, milking the moans and hisses from his lover beneath him. Basking in the tight heat that clenches around his cock and the way Eijirou shivers in pleasure.
“Fuck, fuck, fuck, fuck!” he mutters, feeling himself sink deeper into his rut as his mind zeros in on the submitting alpha beneath him. Katsuki bends over him, raking his nails down Eijirou’s back and watching as the skin beneath reddens from the friction. He resets himself, hands gripping brutally at the red head’s hips before properly mounting him.
He plows into him, quickly picking up speed as the sound of his hips slamming against Eijirou’s ass echoes throughout the room. He’s snarling and growling at the man beneath him, nails biting into his skin and leaving bloody marks behind.
“Ka-Katsuki! Sl-slow down...Kat!” Eijirou chokes out. His insides are being split open every time the alpha above him thrusts into him, driving his cock deeper and deeper inside his ass. The scent of Katuski’s rut suffocates him and he knows the blond has sunk fully into it. The alpha seems to only get spurred on more by Eijirou’s words and picks up the pace. It’s brutal and fast and Eijirou can’t help the sob that escapes him. He feels light headed as pressure starts to build up in his cock, a warm heat overflowing in his abdomen.
He whines, trying to wiggle away from the dominating alpha, an oncoming orgasm rolling into him. But Katsuki is relentless, he continues to slam into him even as Eijirou reaches climax, his legs shaking and shivers rolling through his entire body.
Drowning in pleasure, Eijirou’s thighs are too weak to hold his ass up, so he gets pushed down with each thrust until his hips and thighs are flush against the mattress beneath him.
The blond alpha seems happy with this position, rumbling in approval, his arms moving from his hips to instead rest on either side of Eijirou’s shoulders. He holds him down, slamming as deep as he can into him, his balls slapping against Eijirou with each rough thrust and his teeth clenching together as he hisses and snarls at the alpha below him.
To the rutting alpha, Eijirou was his competition to fuck into submission, to claim as his bitch.
With each thrust Eijirou could feel Katsuki’s knot forming, catching on his rim and forcing the expanding bulge in and out. He almost feels drunk with pleasure as the burn of the alpha’s knot pushes inside him, past his tight rim, spreads his walls. Rolling his eyes back, Eijirou can’t help but press his hips back against the blond, forcing his knot deeper inside.
Katsuki thrusts a few more times, his knot catching and popping on Eijirou’s tight rim with each slide of his cock and it makes the red headed alpha hiss in pain. The alpha above him catches on and shoves his knot back into him one last time, seating his knot fully inside the other alpha’s tight channel.
Choking out a sob, Eijirou feels the knot expanding inside him as Katsuki continues to shallowly thrust, rocking his hips and forcing his knot to rub against Eijirou’s prostate. It’s almost too wide inside him and he thinks he might pass out from the feeling. He shivers and his breath hitches when he’s suddenly cumming, his cock twitching and jerking as nothing comes out. A dry orgasm.
Katsuki is above him, snarling as he jerkily thrusts into him, his knot fully expanded and tightly caught in Eijirou. As he's cumming, his cock twitches with each spurt as he fills up the alpha beneath him, a rumble leaving his chest in satisfaction at successfully claiming his bitch. Placing his chest against Eijirou’s back, the alpha continues to rock into him, riding out his orgasm. His breath is labored and it tickles Eijirou’s skin, but soon enough Katsuki is licking at his shoulder and neck, nuzzling the skin there.
Eijirou knows what he wants and he practically glows in excitement. Tilting his head, he exposes his neck to the alpha in submission.
Purring in approval, Katsuki licks at the skin there, the exposed scent glands, nibbling at the sensitive bundle of nerves.
Eijirou jerks at the feeling and it sets Katsuki off. He bites down on the bundle, ripping into the skin there with his canines and Eijirou practically screams. His eyes clamp shut as he feels liquid fire surge through his veins, his alpha howling in pain and racking Eijirou’s brain with nothing but submit,submit,submit,submit.
He listens and his body goes pliant under Katsuki, mind numb and body too sore to move as he feels more of Katsuki’s come fill his belly. The alpha finally relinquishes his bite and tenderly licks at the bleeding wound.
“Mine.” He growls, and Eijirou knows Katsuki is still in his rut daze by the voice alone.
He nods and gives Katsuki an exhausted smile, “Yours”, he coos before dozing off to the feeling of his husband’s warm body on top of him.