Forgotten Title A Tribe life reincarnation Japanese novel

Like on the title, I remembered the novel is 18+ whose the MC reincarnated into the son of a tribe leader. He's OP and people think he's the blessing to the tribe.

 

MC died from plane and reincarnated
Did missionary position is for concubine/slave while doggy position is for main wife?
Somehow i kinda remember it green tribe or something....

EDIT:
Found it for ya
Green grass of home... Hey it's the title song

Go Search
Grassland law
That's what you want

 

Bwahahaha I have read that novel but I quickly drop it after I read that part.

 

Thank you! Your answer made my past effort of finding it looks like a waste of time! Really helpful!