Ever since he was a young kid, Sora Aoi had constantly traded words of "I love you" with his captivating older sister Aki. As he comes of age, he finds it much more difficult to trade such comforts as they did in those times. Sora finds himself questioning his feelings for his sister, when Aki presents her feelings toward him to rise above a sister's love. Understanding their fondness for one another, they consummate their love-in secret. In a culture that will never comprehend, they must keep their love a secret from everyone else and their family they know. Nevertheless, Sora soon finds himself investigating many kinds of love with different types of girls he met that isn't accepted by society so questioning his feelings for his sister.
Sora is the protagonist of the story. His given name is created as ?? in kanji. He studies in exactly the same high school as Nami, Aki and his sisters. Unlike his sisters, he's not bad at house work and cooking. As he falls unconscious by ingesting even somewhat sake, Sora has a reduced alcohol tolerance.
As a result of questionably difficult relationships together with his sisters, along with his breeding with no father or any male figure in the family, Sora grew up with almost no maleness of all kinds. Nearly all of idiosyncrasies, conduct, and his bearings are those normally expected from a self-conscious girl. His effeminate look makes him an ideal prospect for crossdressing, which he finds himself participating in involuntarily because of the opinion of Runa and Nami's fetish which he loves it. He's quite timid and very much a pushover, and totally lacks the will to stand-up for himself against women, which further enables him to be made to crossdress and sexually approached. Really very much every woman around him is instantly privileged using the possibility to rape him, which some of them did or tried to undeterred by protests and his suffering.
He's profoundly in love with Aki, and does not resist her the second-time she attempts to have intercourse with him, but he does issue himself at times because they've no future in a relationship, whether their incest taboo should be continued. Though with the latter two he was pushed he's also had sexual relationships with others, like Kana, Runa and Nami. After being raped if anything in regards to the sexual assault should actually be taken to to light by Nami, who subsequently threatened Sora with emasculation and departure, he became terrified of her, but promised that he will not despise her. They ultimately rekindle their connection when consensual intercourse was questioned for by Nami, and had since then became more near. With Aki, Sora completely accepts his connection in the last chapters, even defending it against their dad. When their dad takes away Aki, Sora is alone and desires to see her again. After Aki decides to disappear therefore that their love wouldn't hurts Sora, Sora is heart-broken and understands that Aki is really loved by him and needs to be with her. At their mom's grave, they fulfill in the last chapter.