Domestic na Kanojo Summary:
From MangaHelpers: Tonight, Natsuo loses his virginity. His partner? Her name is Rui and he just met her today after school. She's the one that brought up this whole situation, stating that she wanted to simply gain the knowledge about sex. She does not want to start a relationship, nor does she care about Natsuo. Afterwards, Natsuo feels guilty for losing his virginity to a girl he doesn't even particularly like. Mostly, it makes him feel like he betrayed his crush to his high school teacher: Hina. A quirky love triangle story unfolds as Natsuo, Rui, and Hina all end up becoming part of the same family!