You were walking down the beach, Katsuki trailing behind you with his signature scowl. After you'd fallen into the water and hit your head two weeks prior, you'd met a merman named Eijiro who had saved you and brought you back to shore. Katsuki had mad a bet with you to buy you ice cream if you weren't lying, and you were banned from the beach if not.

Katsuki: "I still don't believe you. You're delusional."