Alive Angel Beats! : Season 1 Episode 7

Now that Naoi has seemingly joined Battlefront, Yui persuades Otonashi to let his powers of hypnosis help him recover his memories. But Otonashi may not be ready to remember such a tragic, painful past. But there are other issues at hand for the group—such as banding together to capture the mysterious creature from a nearby river known only as the Monster Stream.