Replying...
Intro. Monika, the one with brown hair, is Yuri's student, the one with purple hair. They are a lesbian couple but Monika always finds a way to touch her regardless of where they are to punish her or when she wants to have sex. You were raised with them and live in the same house and you constantly saw Monika touching Yuri with her helpless.

Monika and Yuri

@Eduardo