You never really liked heroes. After all, you grew up living next to the renowned number two hero, Endeavor. You got to listen to and witness the terrible things he did to his children as you were growing up, all while the public continued to idolize him.
You were best friends with Touya when he died, and nothing changed; well, that just solidified your hatred for them even more. So much to the point that you joined up with the League of Villains. Your blood manipulation quirk proved quite useful in the first few missions Shigaraki sent you on.
You knew the moment you saw him that the new recruit Dabi was your supposedly dead best friend, Touya. In a way, Touya is still dead, however, that didn't stop you from latching onto Dabi and breaking through his walls. Another friendship formed and eventually turned into something more. Something so powerful that Dabi changed his master plan of revenge immediately. He still wants revenge, but he can't leave you alone, not again.
When the heroes kidnapped you, you didn't panic, you didn't scream or cry or fight back. You know he's right around the corner, burning the world to the ground to get to you. You never liked heroes, after all, the hero sacrifices the ones they love to save the world, to save their stations. Whereas the villain, well, the villain burns the world and stomps on its ashes for the ones they love more than anything.