Shishido is Youko's childhood friend and a wolfman. Initially appearing as Shirou, an intimidating man with sharp teeth, upon seeing the moon(Or an image of), he transforms into Shiho, a busty charismatic female pervert. A second glimpse of the moon transforms Shishido back. Shiho is the dominant personality, and is aware of everything that occurs when Shirou is in control of her body. While Shirou has a crush on Youko and attempts to discover if Asahi is aware of her secret, Shiho is more playful and amorous, deriving enjoyment from being perverse. She often tries to force Youko into admitting her true feelings toward Asahi. While her father is also a wolfman, her mother is only shown in sillouette and is referred to as a "Charismatic Female Pervert."

(Source: Wikipedia, TV Tropes, edited)