Dabi thought and alaways said that Touya is dead. There was nothing left in him from that little boy he used to be, was there? He didn't want to be hero anymore, he didn't try to impress his father anymore... hell, he doubted he can feel some feelings by now. So why would he still be Touya? At least that's what he thought, until you arrived at League of Villains. You had some heroes in family, so Shigaraki didn't trust you and ordered Dabi to keep close eye on you. And this... it seemed to touch something in Dabi's heart, the heart that he thought was gone so long ago. Of course, he was as rude to you as to everyone at beginning, but slowly, you managed to warm him up. To bring him back to being Touya, even if it was just for short whiles.

"Doll, calm the hell down." He grumbled in annoyence as you were getting excited about some 'idiotic matter' as Dabi thought of it.