In the final scene of Angel Beats!, we see what we know is Otonashi pass by Kanade. Kanade is humming Iwasawa's last song 'My Song', which she wrote in the afterlife.
How did both Otonashi and Kanade remember this song? If they disappeared in the afterlife, their souls/spirits would have passed on, so how do they remember it?
I assumed that when they are 'reborn' in their next life, they would have no memory of the afterlife or previous life. I guess this isn't the case.