Ep. 12: Kaede's dissociative amnesia returns as she risks losing her current life to recover past memories.

12

Sakuta explains Kaede's condition to Mai and Nodoka: due to the cyberbullying, Kaede started to experience dissociative amnesia. Worried about her, their mother suffered a mental breakdown and Sakuta received the scars on his chest. When reading a note in a book she had loaned to Kotomi, Kaede collapses as her past recollections slowly start to return, though at the risk of forgetting her current life. The Azusagawa siblings try to go to Kaede's school, but the trauma returns when Kaede spots other students. Instead, the two visit a zoo to cheer her up before returning to the now-empty school at night. With no one around, Kaede is comforted by the trip and proclaims she is ready to attend school again. The next morning, however, Kaede's old self has returned at the price of her recent memories. (Source: Wikipedia)