I can't write much because it's a very short episode.
But I can say that you can really see the personality of those characters in this short epilogue.
I really enjoyed it and it's a good bonus to Angel Beats.
I recommend watching it after you finish the anime. You won't be wasting your time.
The art and the sound don't dissapoint even this time. It's one of the good things about this anime.
Even the story it's pretty short, I believe it's enough to complete the anime.
Overall it's a good OVA, if I can call it so, and I don't regret watching it.