Blue Flag

On the first day of the school year at a Japanese high school, Taichi Ichinose, a student, finds that he has been assigned to the same class as his childhood friend Tōma Mita. He and Tōma have drifted apart in recent years, and Taichi is confused to learn that Tōma now hopes to rekindle their friendship. Taichi is soon approached by another student in their class, Futaba Kuse, who tells him that she has a crush on Tōma and asks for his help in getting closer to Tōma. Taichi reluctantly agrees. As Futaba is getting to know Tōma, Taichi and Tōma meet Futaba's protective female friend, Masumi Itachi. Masumi corners Tōma and tells him that she knows he has secret romantic feelings for Taichi, and that she is perceptive about such things because she herself has feelings for Futaba.
Over time, the four characters all become friends. They navigate high school together; Tōma agrees to be cheer captain for the Sports Festival and insists that Taichi and Futaba be his vice-captains, and later they all focus on their college entrance exams. Eventually, a fifth friend is added to their group: Mami Yagihara, a girl who chafes against the sexist double standards imposed on her as an attractive, popular teenage girl. She resents, for example, that while other students can be friends with each other, she is unable be friends with boys without being accused of flirting with them or leading them on. Taichi and Futaba become a couple and choose to remain together even after Tōma confesses his feelings to Taichi. The final chapter contains a time skip to several years in the future, where the reader learns, among other things, that Taichi and Futaba have broken up, and Taichi and Tōma are living together as a married couple.