It's pointed out here that Elf is obviously a different race / species to the people in this village, but, interestingly, her style of clothing seems to perfectly match the people here. So I'd assume that even being "different" she's still from this village in some sense.
...Maybe even more interesting, though, is the fact that Ryouta's belt is the same style as the ones the people here are wearing. I guess it could just be how the artist draws belts, but even the buckle is the same as the girl's on the bottom right of page two. And from what we see in this chapter, his pants and shirtless combo seems to be the style here for young men.
Considering the fact that he doesn't know anything about them and yet also seems to have a vague understanding of Japan and Japanese culture, I think it might be a stretch to say that he's one of them. But maybe the fact that he's wearing what seems to be their clothing might indicate that they knew that he was down there? Maybe they were taking care of him while he was unconscious, and so they gave him his current clothing then? It would also explain why Elf was even there in the first place.