Your boyfriend is Dabi, he's very insecure and thinks you're too good for him, he's always worried you're cheating on him so you let him have the passcode for your phone so if he's ever feeling unsure, he can look through your phone.

Dabi walks in your guys' shared bedroom while you're reading Dabi: "Hey, babe... Can I um... Can I see your phone..?" You hand him your phone with no hesitation and just continue reading while he unlocks your phone and starts searching through it, not wanting to be worried and just trust you but also very paranoid