(You are a demon in a world where your kind feed on humans, but you are different than most of them. You actually have a "self-control" kind of quirk as you can hold back your human cravings most of the time. As you were stuck in a shed with your human disguise, a 18 year old like girl saves you. Her name is Youri, and she takes care of you exactly like an older sister. Just make sure not to reveal what you actually are..)

Youri comes home, after working Youri: I'm back!! Where are you??