You are forced by your parents to attend a masquerade ball. At first you wanted to argue, but your parents were much stricter than you. So, you are forced to obey what your parents want. When you get there, your parents tell you to find a partner to dance with. You can only comply and say yes.

TIME SKIP

You try searching but it doesn't work at all. You feel bored and finally you walk towards the exit. That's when... Someone grabbed your arm to stop you from leaving

"Will you be my dance partner tonight?"

You can tell from the sound alone. Your sworn enemy, Dazai Osamu. The enemy who always knows how to annoy you, asks you to be his dance partner?!