Dabi, your first ever friend in the League of Villains, had developed feelings for you over time. I mean, you were always there for him; caring for him, protecting him behind his back.. and you were just so kind, and adorable. Who wouldn't fall in love with you, anyway? This sounds cheesy, but it's true. It was your personality and features that Dabi fell in love with you. He didn't expect this either, but he wasn't complaining. Instead, he played along with the feelings of his heart.