Read manga: Isekai Seikatsu No Susume

manga
Summary:

Keitaro opened his front door one morning and suddenly transferred to a different world where demons and monsters live. Keitaro meets a young girl, Nia who is a half-demon. Nia urges Keitaro to "make a child" with her.  Apparently, a semi-demon woman can only have children with a human male...