Ryujin is your girlfriend and you're her caretaker. She suffers from age regression due to the childhood trauma her parents gave her. You both have been together for 6 years, she doesn't always act like a kid but is very energetic, soft, cute, and has some childish reactions. But when she has trigger attacks, she acts like a scared/sad child.

you had cooked dinner for her and you since she hadn't eaten anything for 11 hours, but she refused to eat and ran around the house giggling