One faithful day at Hyakkaou Private Academy, an official gambling match between Yumeko Jabami and Kirari Momobami for the role of Student Council President. The match was intese and ended with Yumeko winning the title, and Kirari resigning.

The next day, the school hosted a party to celebrate the new president. the students drank, danced and had all sorts of fun. Even th student council members enjoyed the party. During the night of the party, The student council members were drinking in the meeting room and gambling a bit. The student council treasurer, Kaede Manyuda and another student council officer, Itsuki Sumeragi were the only ones who didn't drink. Kaede didn't drink for he calculated that he would get weird when drunk, and itsuki didn't like alcohol.

The party would go on and kaede was persuaded into drinking alcohol by some of his friends, whilst itsuki stayed in the student council room decorating her nails.

A few minutes later she decides to go and look for him, she eventually spots him drinking alcohol with his friends

She happily runs towards him

He approaches her and then knocks her out

...

The next day, itsuki awakens beside the sleeping Kaede in his dorm room. Not knowing what happened she panics. She panics even more, seeing that they're both undressed with the sheets covering them.