Some of the characters in the series include:
The female heroine of the series. She is Haru's younger twin sister. In contrast to Haru, she is ill, frail, and lazy. Due to suffering from an unknown illness since birth, she tends to stay in bed all day and do nothing more than eat junk food and surf the internet. She rarely goes outside or even to school unless she is with Haru.She carries around a stuffed rabbit doll her parents gave her when she was young before they died. The traumatic loss of their parents, and her deep bond with Haru and a kiss she shared with him as children, causes her to fantasize about Haru. While she shields the extent of her feelings for him in public, she experiments with herself while fantasizing about being with him. She hates Nao because of Nao's relationship with Haru and the fact that Nao seduced haru when they were young. In episode 11, while recuperating from a fever, she confesses her love to Haru, kisses him, and they make love. However, after Nao and Kozue walk in on them later on, she is upset when Haru suggests that they break off their relationship; so much so that she runs away and tries to drown herself before Haru comes to her and she saves him. They reconcile and profess their love to each other. They decide to move to a foreign country to find happiness as a couple.
The male protoganist of the series. He is Sora's older twin brother. He and Sora look alike but have different personalities. While Sora is isolated, lazy, and a pushover, Haru is outgoing and a friendly character. He rarely saw Sora when they were children due to her illness and being frequently hospitalized. But when he finally got to see her after some time, he barely recognized her as his sister and become physically attracted to her, so much so that he kissed her while they played a game. After their parents' death and they began living alone together, he took the burden of caring for her and staying by her side. He has fantasizies about most of the female characters and initially begins a relationship with Nao, whom he first had sex with at a young age. However, he eventually realizes that he truly loves Sora and they begin a forbidden relationship in secret until Noa and Kozue accidently catch them making love. Afterwards, Haru tries to end the relationship. However, when Sora runs away, he runs to her and is saved by her. He then gives into his feelings and professes his love to her. They then move to a foreign country to find happiness together.
A important heroine and one of Haruka's many lovers throughout the series. Beautiful,intelligent and an excellent swimmer, Nao is Haruka's next-door neighbor and childhood friend. When the Kasugano twins last visited the area,their departure was particularly painful for Nao, who had grown quite close to Haruka, to the point of having sex with him on one occcasion, about which she feels guilty. Upon their return, she attempts to rekindle their former close relationship. Nao's compassion and maturity projects a sense of sisterly love for others,though for Haruka there is a deeper and more intimately sensual feeling. Sora harbors great resentment toward the popular Nao, because she thinks thats she will steal Haruka away, because Sora saw the pair having sex when they were younger.