Responses
I think they'll do it once Kiri grows up into an adult yokai, because only then it won't be a problem to go back and forth between the human and yokai worlds.
http://www.mangago.zone/read-manga/heart_pounding_excitement_at_mononoke_girls_a/tr/93492/page/133/
I felt like she says "Once you grow up, let's do it" cuz she's beet red, lol.
She proposed so they will and theres always toys.
Im a bit miffed that they will never "touch mouths" ever, but its still a cute story just has a lot of holes in the plot and a too rushed storyline.