Oni ga Deru ka Ja ga Deru ka - Vol. 1 Ch. 4

[MangaDex]

 

[Lynkaster]

now, what kind of youkai is naturally despised by girls... goblins can be counted ? x'D

 

[Blackkid121]

F

 

[tgb089]

""Relying upon your grandfather..."
So, has he been boning all the ladies in the village? Sweet gig.

 

[saphirekosmos]

... is no one going to point out that the 3 "brides" are most likely his aunts?

 

[justforthelulz]

Grandpa was living the harem MC life, up until he died. What a player.

 

[greatninja3]

Grandpa has been living the dream I guess all of the girls are his aunt then

 

[UncleRad]

After seeing all the comments below about the bloodline relationships between all the different species of female youkai and the MC's males, one thing became quite clear: It's a cultural misunderstanding.

The Grandmother in the story is more like a social rank than a biological one. Otherwise this will practically be like incest if the MC ended up marrying and having kids with his mom's sisters.