Ao no Binetsu

Mana lives on a southern island where her brother-in-law, Kakeru, has been pressuring her for two years. After meeting Akihiro while swimming, he transfers to her school, and they begin dating. Despite Akihiro's cheerful and kind nature, Mana's difficult situation with Kakeru remains unchanged, and the secrecy causes her pain. Akihiro grows suspicious of the tension surrounding her. At a summer festival, Kakeru appears with his childhood friend Ayano, who questions Akihiro about Kakeru's feelings for Mana. Akihiro intervenes, claiming Mana as his girlfriend, but Kakeru becomes angry, attacks him, and then grabs Mana in front of him.