Imagine person A of your OTP doesn’t usually like eating chocolate or sweet things. However, recently they have been having a craving for them. They are a little embarrassed by this, and the treats they’ve been craving are person B’s ‘private stash’, and so they don’t tell B, and only take at night when B is less likely to catch them.
Meanwhile, B is becoming extremely confused as to where all their treats are disappearing to.
Bonus: B hides away in the kitchen one night in an attempt to work out what’s been happening, and catch A in the act.