Pre-review:Village's Ritual is an adult manga series about an anthropologist (or a merchant of artifacts, as he calls himself) who seems to have a dark past and his beautiful and carefree assistant going through a serial of murder & mysteries cases.
This series is still doing great.
This time we learn more about the MC's 'lost' girlfriend and what had happened to her. That I'm glad.
This volume is more sexual than the previous volumes, I don't mind it all that much but at time the sex and the nudity does look very show-off-ish and serves as a gimmick to draw readers' attention (or it can be the manga-ka just simply enjoys drawing nudity and NC-17 stuff).
As to the explanation for the sex rituals in that remote island, I think it makes sense in a way, plus it does introduce us to the social and ritualistic meanings of sex rituals in ancient time, etc.