Aneppoi no: my sister, like sister

Mutsumi Natsukage, or Mutsu-nee for short, is my cousin who's "like an older sister, but not my older sister" and she's a university student. She's freeloading with us because it's convenient for her commute. Anyway, Mutsu-nee and I are close and her skinship is relentless. She comes over to my room