@samhill I think it is for mental fatigue. Like how having a good dream makes you feel better? Technically wet dreams do make the person better i think... so i guess they are a little the same?
Do you know how in every fantasy manga there is that one hybrid character with an epic but short (very short) backstory of their parents being star-crossed lovers? THIS IS THAT MANGA.
If I could buy Onio-sensei's work I would but since most of sensei's readers are probably online It's no wonder they have not much publicity for their amazing works... Sigh~