......we'll be up to our armpits in utsuho in a century or two, unless its EXTREMELY rare for utsuhos to be born. ..... Which is kinda what the artist seems to imply, with how there were no utsuho ko's....
Though I've never explicitly addressed it, that is indeed what I mean to imply - the birth of an Utsuho is a statistical freak accident, substantially rarer than the birth of any hybrids.
That's in addition to the stigma attached to Utsuho from other yukkuri due to the inherent danger of being near one when they die. Thus it's rare for them to even mate.
I think that what Kodoku showed here is one of those "no win" scenarios, yeah Utsuho may be able to kill humans and stuff, but this is clearly a scenario that she can't do anything about, not only doesn't know the face of the abuser, but neither she knows a good way to track the guy down or anything.
It's really, well, a dead end in yukkuri capacities, to track down someone without seeing that someone and following him or her.