Following Natsuki Enomoto's confession rehearsals with Yuu Setoguchi, their younger siblings Kotarou and Hina struggle to confess their own love. Despite a disastrous first meeting in middle school with her upperclassman Koyuki Ayase, Hina’s heart is captured by his warm smile. Initially confused by these newfound feelings, Hina soon realizes that she has fallen in love for the very first time. Chasing after her brother Yuu and her crush Koyuki, Hina also enrolls in Sakuragaoka High School; but the threads of love are far-reaching, and they entangle Hina and her friends. Boisterous but sensitive, Hina hopes to confess her feelings to the tender-hearted Koyuki. Meanwhile, Kotarou, oblivious to his own feelings for her, is determined to always keep Hina smiling. This movie follows Hina, Kotarou, and Koyuki in high school. Their youthful love forges new relationships, but also threatens to break others.