He couldn’t tell you what started the fight. After a while, it didn’t matter - once they started screaming at each other, they couldn’t stop. Kurt is sure that most of the things said have nothing to do with what the fight is actually about. It turns into a list, almost, of everything they hate about the other, a list that shouldn’t be as long as it is.

It seems to happen all the time now, the fighting. He picks fights when Blaine drinks. Blaine is angry when he doesn’t drink, and sad when he does. No matter what there’s always something wrong, and Kurt doesn’t know when it began or how to fix it.

And it just doesn’t stop. They’re in each other’s faces and screaming, and Kurt wants it to stop but can’t. There are tears streaming down his cheeks and his words come out more like sobs than anything intelligible, and he has to stop this, he has to be the better person and walk away and let them calm down until they remember that they love each other. He knows this, but he keeps on screaming. Finally, he bursts out, “Just because you’re too much of a fucking coward to deal with your own mistakes, just because you’re too scared to start a day without a drink -“

The force of the slap echoes in the sudden silence of the room. Kurt can’t breathe as he lifts a hand to his stinging cheek. When he looks at Blaine, all of the anger has drained out of his now ghost-white face. Now he stares at Kurt in horror instead of rage.

“Kurt,” he whispers. His voice quivers, small and quiet as if scared that if he speaks too loud something will break - but it doesn’t matter. Something is already broken, and probably has been for a long time. Blaine is not abusive, and this is, more likely than not, a one-time mistake. But added on top of everything else, the anger and the hurt -it’s the straw that breaks the camel’s back. “Kurt, I-“

“Get out.” Kurt says. It almost scares him how calm he is, methodically severing the ties to the man who has been his entire life since he was seventeen.

“I’m sorry -“ Blaine reaches out, as if to offer comfort, and Kurt automatically flinches back, nearly tripping over his own feet. Never in all their long years together has he been afraid of Blaine. Not until now.

“Get away!” Blaine backs up, wrapping his arms tight around himself, and there are tears in his eyes now. He knows how much he’s screwed up. And Kurt just doesn’t care. Can’t find it in him to care, anymore. “I said get out of my house.” His house now, not Blaine’s, not anymore. Kurt’s voice is utterly cold. He can still feel the impact of Blaine’s hand on his cheek.

Blaine steps back through the door, openly crying, shoulders shaking with repressed sobs. “I’m sorry,” he repeats, and Kurt’s heart shatters all over again. “I’m sorry, Kurt, god, I’m so, so sorry…”

“Not as sorry as I am.” He slams the door. He can hear Blaine crying outside for a long time afterwards, deep, wrenching sobs that tear straight through him. Kurt sinks down to the floor, all previous coldness gone and replaced with simple exhaustion, and lets the tears come again, rolling hot down his cheeks.

Eventually, after the sounds of his crying have faded, Kurt hears Blaine walking away, his footsteps growing fainter every second. Eventually Kurt’s chest stops heaving, and he wipes his face and breathes in deep and stands, going to the other room to see if they woke three year old Amelia with their fighting and sooth her back to sleep. He doesn’t answer the five messages Blaine leaves on his voicemail throughout the night, not when he can still feel the imprint of Blaine’s hand on his cheek, even once it’s stopped hurting, for hours after.

Blaine will come back, eventually, and he’ll try to talk, he’ll half-heartedly suggest that they try to get some help, maybe hire one of the marriage counselors he’s always scoffed at. But Kurt knows that it’s too late.

It’s over.