>>732191I've been thinking about this question for a while to be honest, lol
When Leliel and Avnas (His name was Amriel, at the time) were in Heaven together, right before the fall, I think Leliel regrets not saving Avnas from his fate. I think now that he's found him though, the sentiment is only intensified knowing Avnas doesn't remember him at all anymore.
I think Avnas is past the point of regretting, he wants to make up for his mistake and has no choice but to do whatever it takes.
In the moment of this drawing, Leliel heals Avnas's wounds, and in turn, he restores his memories of Heaven, and of their relationship as well. Up until then, Avnas has only seen Leliel as an annoyance, some guy who had always bothered him, and someone he honestly wouldn't think twice about. Once his memory is restored, he's conflicted, and contributing to that, and where he finds himself now, is a significant feeling of regret.
https://youtu.be/qwhDDPxJZwo 