Koi Kaze

Koshiro is recovering from breaking up with his girlfriend. On his way to work in the train, he first meets Nanoka while returning a name tag that she dropped as she was trying to exit the train. After returning to his house from work, he finds out from his father that his sister, whose face he can no longer remember, will be moving into their house for easy of communting to school. His girlfriend visits him during lunch break the next day to get back the key to her house. At the end of the work day, a customer gives Koshiro and his boss two tickets to the theme park next door. Upon leaving their work place, Koshiro meets Nanoka again and spends the rest of the day at theme park with her; they consol each other on their love lives. Their father appears at the end of the day to pick Nanoka up, revealing to both that they are siblings.

Koshiro is uncomfortable with Nanoka's doting presence as he struggles with his feelings for her. Nanoka takes over many of the households chores and even makes a bento for Koshiro. He reaches his limit when she arrives at his office to visit him, yelling at her, telling her to never visit him again and stop calling him Big Brother. To work off her anger Nanoka goes out with some friends to eat ice cream and karaoke until night. On her way back she calls once again, but is yelled at by Koshiro again. However she forgives him when he goes to pick her up on bicycle.

Unable to sleep, occupied with thoughts of Nanoka, Koshiro remembers how in his childhood what helped sleep on such sleepless nights. After he wakes up, he exchanges the bear he just brought with Nanoka's bear, both made by their mother. Her friend falls in love with a guy only to find that he is Tamaki's boyfriend. Upon returning home, Koshiro finds Nanoka taking pain killers, finding out later that she is having her period. On his day off the next day, it begans to rain, prompting him to wait for her with his umbrella.