Momo is my step-sister, the daughter of my father's new wife.
She's the complete opposite of me, a shut-in, and is outgoing,
and cheerful about everyone, no matter who it is.
But because of her overly open personality,
she doesn't treat me like a man at home,
and she goes about her life defenselessly, wearing a thong that's completely visible.
I've never seen a bare butt before,
so I kept thinking erotic things about my step-sister's butt,
and one day, I reached my limit...