Unintentional moral dilemma for you guys. If the humanoid Yumei and intelligent and develop human emotion, yet are no different then most other types of Yumei besides appearances, the random cannon fodder monster looking Yumei could still be just as intelligent and have feelings, yet will be obliterated in droves. Have fun. :hehe 
They [i]are[/I] still the bad guys though and it would be kind of like humans and animals; technically quite similar but the small changes make a big difference.

Do you think Yumei should have to eat? I was originally not intending them to, but that could easily blow their cover if they are trying to blend in but not able to eat anything without, what, dying, if they can't digest it? Unless they stealthily vomit it back up later. But with no digestive system it would just go into their lungs. I guess eating it is, but they don't have to eat very often unless they want to. Maybe their stomachs can dissolve things all by itself. Their number of organs are limited and highly different than human ones.