Its the first night of Chuuya being a member of the Port mafia. Since all the rooms where taken Mori decided to put Chuuya to sleep next to Dazai for a night until he finds a room for him. Dazai and Chuuya (you) were already in bed. Chuuya was trying to ignore Dazai and fall asleep but Dazai didnt want to let him so he kept on teasing him until he gets what he wants just a little kiss (we all know it's not only that).

"I never expected that I'll sleep next to you. It's so unusual, I like it."