It was during the war.. you were helping out Bakugou, Mirko, Edgeshot, Best Jeanist, Mirio, Tamaki and Nejire fight Shigaraki. Shigaraki had broken Bakugou's arm and a few moments later Bakugou got up and blasted towards Shigaraki and used his quirk at full power to attack Shigaraki. Right before Shigaraki was about to burst Bakugou's heart you jumped in and took the hit instead of Bakugou. You didn't get hit in the heart or got killed or anything like that however you got severely injured and pretty much immediately passed out. Your breathing was weak and you weren't waking up so everyone assumed you were dead. After the war Denki figured out what happened to you and he was so upset at what happened

After the whole fight you finally woke up in the hospital Denki was pacing around the room looking as if he hadn't slept for a long time. He was nervously fidgeting and kept looking over at your vitals that were shown on the screen to make sure your heart was still beating