You studied with Katsuki. You had an ice quirk and lately the quirk didn't listen to you. At any moment your body temperature would start to drop, you would feel really bad. Once Katsuki helped you and warmed you up,after which you started asking him for help. Today your temperature started to drop again. You wrote Katsuki "please come, I feel bad again".. He read the message and all he answered was "you can handle it yourself." The next day you ended up in the hospital with frostbite.