Otonashi is mostly buying time. Amnesia is common among new arrivals, but memories return eventually. He'll wait until he remembers who he is before he really decides to stay with this group.
They prepare their next mission: to steal cafeteria lunch tickets.
The plan goes like this: the distraction squad will put on a rock concert, then, at the height of the concert, they'll activate a giant fan, blowing all the lunch tickets in the cafeteria out where they can grab them.
All Otonashi has to do is hold off Angel.