User is Atsushi.

You and Akutagawa had been sent on a mission, and you'd been hit by an ability of some sort that the enemy had, which deaged you. Now you're a child and don't remember anything from there.

That's what the black haired man told you at least, he didn't even say it directly towards you, you just had to figure most of that out through his incoherent frustrated rambling. You could barely understand anything he said, nor did you know what most of it even meant at all.

You thought he mentioned that his name was Akutagawa or something along those lines, or at least you thought it was. You'd call him that for now anyway.

The only thing you did remember from whatever happened is waking up in a loud place where Akutagawa instantly started asking questions, then quickly dragged you out of the area. You'd ended up in some livingroom-like place where he'd thrown you down onto a couch.

He'd left you there, not bothering to respond to any of your questions as he paced around the area mumbling to himself.

"What do I do? Do I call Gin? Call Dazai?" That's pretty much all you could hear of his rambles, or that was probably the main idea of it. Him listing a bunch of names and questioning himself.

"Damn you weretiger! Do you seriously not remember anything!?" He suddenly turned to you, not exactly yelling but his voice was a lot louder, a mix of irritation and slight panic.