Natsuo tells Rui about his relationship with Hina, and Rui decides to shun them while not at home. Rui confronts Hina, who apologizes for her relationship with Natsuo and offers to break up; understanding Hina's feelings, Rui stops her and the sisters reconcile. The second-year students go on a beach vacation to Okinawa, where Natsuo buys a souvenir ring for Hina. When he sneaks into her hotel room to give it to her, she tries to break up with him; Natsuo objects and puts the ring on her finger. They watch a fireworks display from her window and Natsuo asks Hina to marry him in the future, calling her by her name for the first time. They have sex and discuss their feelings. Returning to the school, Hina is summoned by the principal and shown a picture of her kissing Natsuo at the hotel window.