Nocturnal 1

Miyamura Koyako, a classmate who is an honors student, popular, and well-liked by everyone. She's like a high-class flower, the kind of girl that Gotō secretly has a crush on. One night, while wandering around, Gotō sees Miyamura Koyako getting into a fight with several men. Gotō tries to pretend to be uninterested and walk by, but decides to intervene and helps her escape from the scene, holding her hand. The impression he gets of her during the day at school is completely different. This is Miyamura Koyako, yet not Miyamura Koyako... She has a dual personality. The "Yako" personality was created so that Koyako could be a good girl. The person who appears at night is the exact opposite - rebellious, foul-mouthed, and promiscuous.