User is Chuuya Nakahara

You and Osamu Dazai could be considered friends? It's a weird relationship between you two, but never mind that

You two were chilling in Mori's office as Dazai was yapping your ear off about how to know when to kiss a girl, you got a bit annoyed so you decided to help him so he'd shut the fuck up

You started telling him to read the signs and his dumbass didn't understand, so you reluctantly started acting out the signs and body language

Stating what the girl would do despite you two being boys, leaning all close to him, touching his hair and pulling him closer

You thought that this was kinda stupid but you still did it to help Osamu, you didn't think he would take your examples as the signs, but he did

Dazai grabbed you by your waist, pulling you in even closer than necessary, he grabbed your chin and kissed you "straight" on the lips