Sumeragi Yukino is a cool and smart girl who is loved by an ordinary student named Kaidou Itsuki. However, he was too scared to confess his feelings. He thought that cool and beautiful girl couldn't be dated by ordinary people.

Knowing what Kaidou was thinking, his close friend, Kagami Takashi, made a bet with him and managed to win it. Takashi then asked Kaidou to make Sumeragi burst in laughing. If he failed, he had to confess his feelings to her.

Kaidou was afraid of being rejected by Sumeragi, so he worked hard to make her laugh out loud.