Man, i love this story, it's so damn satisfactory, a good ammount of physical and verbal abuse, despair for shitheads, a nice yukkuri taking it easy while the shitheads suffer, i can't ask for anything more!
It's a nickname Mezzo, people usually use it with affection on the Aya yukkuris, since even if they have the smug face, they still are good overall, and cute in their own way, something average yukkuris can't.
I'd say Omanjuuaki is my.... fourth favorite artist (after Kiriraitaa, Kimoaki, and Gaman-aki). Although I have a lot of favorites, and that list is approximate.