Koi Kaze [GrimRipper] Dual Audio

Twenty-seven-year-old Koshiro Saeki, who lives with his father, is dumped by his girlfriend of two years, who claims he was too cold and she'd found someone else. While on a train the morning after, he sees high school student Nanoka Kohinata looking at a button and crying. As she's later getting off the train, she drops her wallet and Koshiro follows to return it. 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 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'd loved 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 it is closer to 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 to rid himself of the attraction that he felt for Nanoka when he first met her. Instead, his love and desire continues to grow, despite his attempts to fight them. Entering womanhood, Nanoka also develops feelings for her brother, only increasing Koshiro's struggle. In near desperation, he moves out of the family home to remove himself from temptation and attempts to keep his coworker, Kaname Chidori, from finding out the truth behind his brusqueness with Nanoka.

However, the solution is only temporary, as Nanoka begins visiting regularly, cooking him meals and spending time with him. Eventually, unable to resist their feelings anymore, they have sex. Unsure what to do now that they have broken a societal taboo, they visit their parents, before contemplating committing suicide together. In the end, they decide to live, and to continue their relationship.