This really is one of the few series where a harem ending makes practical sense. However, won't the village still run into a problem from a lack of genetic diversity, as well as declining population due to some being "unchosen"? Unless Yokai are different in those regards... I mean, we already have examples of Yokai spontaneously existing from gaining sentience, such as Miku and Suzu. I also highly doubt Yuu's Grandfather is responsible for creating all the younger generation, right? Though, they did say there hasn't been any males in 100+ years, right?
Whatever... Overthinking it just makes it more complicated and I'll just end up with more questions than answers.