Tomoru, a high school student, meets the older and cheerful senior Yaeko by chance at school and quickly falls in love with her. To his surprise, Yaeko turns out to be the older sister of Saki, his close friend. As Tomoru grows more fascinated by Yaeko’s bright and domestic personality, he one day stumbles upon something shocking in the classroom that hints at hidden depths and secrets. This discovery sets the stage for a tangled love triangle among the three, forcing Tomoru, Saki, and Yaeko to confront their own feelings and pasts. The story unfolds in a contemporary school setting, gradually revealing the reasons behind each character’s actions and the unspoken tensions that exist between the siblings and their friend. As misunderstandings and distance grow between Tomoru and Saki, Yaeko becomes the one who tries to bridge the gap, leading to a final resolution of the trio’s intertwined emotions and the secrets that have shaped their relationships.