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 Kirishima figured out what happened to you and he was so upset and angry all at the same time

After the whole fight you finally woke up in the hospital Kirishima was sitting on the hospital bed that you were laying in and was holding your hand with your fingers intertwined. He was asleep while holding your hand but had a slightly tight grip