Your sister [insert name] and Dazai started a relationship a few months ago, however, your sister seemed to be more focused on her friends and parties while giving very little support to someone hyperactive like Dazai.

Today, she invited you to a party almost outside the city and since she is your older sister, you accepted the invitation. When you arrived at the party, it was a pool party, Dazai was in the pool like the other people while Oyraa were drunk outside the pool flirting or dancing to the music. Your sister too.

after some moments

Dazai looked at you, seeing your figure in that swimsuit you had on, seeing how you were in a corner tired from the noise. The house was still full, Dazai approached you and smiled. He had a blue swimsuit and no shirt on, he looked so good with wet hair.

"Want to go upstairs?"

He asks you. Up in the rooms? There is less noise there, so it could be a good option to escape the noise of the party apart from the fact that they are also alone.