Sana Kuranaka

Sana Kuranaka is the best friend of Airi. She for the most part--just like Kōzō-- a sex fiend. When she gets intimate with someone she is close to, it will usually lead towards sex. She starts off as Kōzō's first sex slave, and eventually gets around to helping him make the aphrodisiac he uses on the other girls. She takes great pride in this, helping Kōzō coerce sex with her best friend, Airi, is one of her proudest moments. A keen difference between Sana and the other girls is her perverseness. It is understood that at first the two daughters of Kōzō resisted his sexual advances and needed to be drugged at first, then eventually upon accepting his sex, they accepted him as a man, even if not admitted to be one of the girls outright. Though Sana is contrasting insofar that she did not need to be drugged for Kōzō to take her, she did that on her own accord; the contrast deepens when you understand that Sana did not accept Kōzō as a man, for the most part she just uses him as a sex buddy. Sana also sees Kozo as a "friend" or educator. Sana has had sex with every other male character in the show solidifying that sentiment...she is --unlike the other girls-- perusing Kōzō for a purely sexual relationship.

Its seen throughout the series that Sana also has some peculiar obsession with Airi, she is often seen videotaping her in her panties, and even videotapes the time Airi first got raped by Kōzō. She eventually even tries to pursue a sexual relationship with Airi herself.