Angel Beats!

Yuzuru Otonashi awakens in the afterlife with no memory of the life he lived before dying. He soon joins the SSS, a group fighting against Kanade Tachibana, known to them as Angel, whose purpose appears to threaten the inhabitants of this strange world. As Otonashi tries to survive the conflict, he also searches for his missing memories and a clearer understanding of where he is. The more he learns about the afterlife and the people around him, the less straightforward the battle begins to seem.