Aki Sora revolves around Aki Aoi and Sora Aoi, a pair of close siblings who have shared an intimate bond since childhood. During their coming of age, they each come to realize the true depth of the love they feel for each other and consummate that love in secret. They keep their sister, Nami, Sora’s twin in the dark about their new relationship. Nami, clueless of what is happening in their household aims to set her brother up with her best friend, Kana Sumiya. Despite these relationships Nami seems to have feelings for someone near to her too but keeps them secret.

Overtime, Sora met with other girls who took a liking to him, and had sexual encounters with them as well. Nami, who became psychotically jealous of Sora for taking Kana, ended up raping Sora and threatening to sever his penis if he told anyone about the rape. In Chapter 15, she induced Sora to have consensual sex during which he felt gulity kissing her and she seemed to regret the deed afterward.