is a Japanese manga series written and illustrated by Motoi Yoshida. It was published in Kodansha's seinen manga magazine Evening from 2001 to 2004, with its chapters collected in five tankōbon volumes by Kodansha. The series tells of the taboo love affair that develops between 27-year-old Koshiro, and his teenage 15-year-old younger sister, Nanoka. It was adapted into a 13-episode anime television series by A.C.G.T. Directed by Takahiro Omori, it was broadcast on TV Asahi from April to June 2004; only twelve episodes of the series aired, with the remaining episode streamed online and later included in both DVD releases and when the series aired in reruns as the eighth episode. The anime series was licensed for release in North American by Geneon Entertainment, which released three DVD volumes in 2005. Synopsis Twenty-seven-year-old Koshiro Saeki, who lives with his father Zenzo, is dumped by his girlfriend Shoko of two years, who claims he was too cold and she had found someone else. While on a train the morning after, he sees high school student Nanoka Kohinata looking at a button and crying. Later, as she is getting off the train, she unknowingly drops her train pass and Koshiro follows to return it to her. Koshiro finds himself watching her sudden smile as she notices the cherry blossoms are in bloom. Later, Koshiro is leaving his job at a marriage-arranging company with a coworker when he encounters the same girl again. Having two free tickets to a nearby amusement park, he gives them to her. To his surprise, she asks him to go with her. While on the Ferris wheel, the girl explains that she was crying on the train because she'd been rejected by a boy she had been in love with for several years. Koshiro ends up telling her about his own break up, and cries while she comforts him. As they leave the park together, having enjoyed the outing and expecting to part and never meet again, they run into their father and are shocked to discover they are siblings. Nanoka moved to Tokyo just that morning to live with them because their home is closer to her new high school. As Koshiro hadn't gone home the night before, he hadn't learned of her arrival. Since they had grown up living separately, they didn't know what the other looked like. As the series progresses, Koshiro finds himself unable