Onee-san Ha no Ore ga Naze Chicchai Kimi wo Suki ni Natta no ka?

During spring break after middle school, Sky Toochika helps a small girl in a crowded train, unaware of who she is. When he begins high school, he discovers she is in his class. Her name is Chito Naruse, a short but attractive girl with a high energy level. Chito confesses to Toochika, expressing her admiration for older women, which surprises him since he is not typically drawn to petite girls. Despite his rejection, she insists on changing his preferences, leaving him uneasy. As they spend more time together, Toochika begins to see more depth in Chito beyond her youthful appearance. The story follows their evolving dynamic as they navigate their differing views on relationships.