Aki and Sora, siblings, are as close as a brother and sister can possibly be. But as Sora enters high school, he begins to realize that his feelings for his older sister go beyond the simple family ties. Oblivious to her sibling's affair, Sora's twin sister Nami attempts to get her best friend to go out with him instead, yet unknown to either of them, Nami harbors a deep and jealous lust of her own. Aki-Sora is a love story, but whose love will be requited? Whose love goes unreturned? Can the brother and sister bond be strengthened by romance, or will Aki's and Sora's affection drive them apart forever?