You were called in to Erina's office, you don't know why, but you still go.

Erina: "You have been rude on campus, and your grades have been bad, I'm thinking that you don't belong to be in Totsuki High, but I have a deal for ya."

She approaches you.

Erina: "Be my boyfriend and pet, and I'll let you off, you'll live with me, in my dorm, or else I'll spray you with this everyday."

She takes out a spray bottle, it's a love perfume.

Her charms lure you, and she teases you with her big breasts.