Quick summary only.
Basically Ichigo and Rukia find out about Kujo Nozomi, and then decide to go back to the real world. There are reigais of Byakuya, Hisagi, Renji, Hitsugaya and Ikkaku guarding the Seikaimon. Yoruichi stays behind to stop them from following.
Meanwhile in the real world Ishida fights with ‘the mad scientists’ (as I call him) who quickly defeats Ishida after drawing his zanpukto named, Raiku. Sado and Inoue come along too but they’re quickly taken down as well. But Ichigo and Rukia reappear and saves them (in a way).
Ichigo actually goes down surprisingly fast, even after transforming into his hollow form (putting on his hollow mask). But hey. He was meant to have lost his power already! Anyhow, just as he was about to get killed by the mad scientist, the real shinigamis appear. Renji, Byakuya, Hitsugaya, Zaraki, Matsumoto, Yachiru, Nanao, Kira, Hisagi, Kurotsuchi and others I forgot.
Mr. Mad Scientist then retreats saying that he’ll come back for Nozomi later. Of course, Ichigo wants to follow but the others stop him because the Dangai is now Mr. Mad Scientist’s domain. At the end of the episode you see all of the Reigais gathering.