Ryouko

Ryouko was created as a substitute teacher for Yamaku by the devs. She was referred to as a "semi-joke character" that was mostly talked about on the IIRC channel. She makes no appearance in the game itself nor is she mentioned.

Ryouko was based on the title character from the Visual Novel Sumeragi Ryouko no Bitch na Ichinichi.

In the original visual novel Sumeragi Ryouko no Bitch na Ichinichi, Ryouko was a dedicated teacher at a private academy who was also a nymphomaniac that slept with her male colleagues and sometimes her students.