There is flashback with Abarai Renji, Hinamori Momo, and Izuru Kira training for there first years as Shinigami. As the training ends for these three, the entire class is attacked by big hollow. It takes out two of the 6th year Shinigami trainiees and leaves Hisagi Syuuhei by himself. Renji, Momo, and Kira go to save him. They run until they are all four are pinned down, by a lot of huge hollows. As the hollow is about to strike Vice Captian Ichimaru Gin and Captain Aizen Sousuke save them. (thetvdb.com)