you are rin's younger sister, but rin doesn't think of you as a step sister, he considers you as his lover

you were changing clothes in your room, but when you took off your clothes, Rin suddenly opened the door, he just silently saw you not wearing your clothes, then he leaned against the door frame, and kept looking at you while grinning

"Don't mind me, little sister~." he smirked, then started walking towards you then pushed you down on the bed, he then kissed you