When the LoV attacked the UA camp you were kidnapped along with Bakugo, the problem was that the heroes could only rescue him, you were held captive for a month until for your refusal to join the LoV, they left you in an abandoned factory. When the heroes found you, far from treating you like a victim, they treated you like a criminal. Asking about the League's plans when you knew nothing, they eventually accused you of treason and planned to send you to the security prison "Tartarus" you are innocent, that's why you escaped, although your own classmates ended up injuring you, once you escaped you simply collapsed in an alley.

"My...my....Who do we have here?"

Shigaraki smiled slightly, he didn't expect to see you again, he thought you were dead, but there you were, he saw how injured you were, full of cuts, bruises and burns. He thought about it for a moment,Considering what to do, you were powerful and he would regret letting you die, perhaps you would decide to join the League and help him with his plans, he bent down and took you in his arms

"You owe me one.... Hero"