Three Lives of Reincarnation, All Beasts

Basically, the story goes like this: After the protagonist dies, he gets three chances to be reborn while retaining his memories. But the price is... he has to appear in the form of a 'beast'! He might be a loyal, ordinary dog, a terrifying-looking beastman or monster, or perhaps even a mighty, imposing dragon!

Anyway, it's about all sorts of amusing things that happen between the male protagonist and his three mistresses. And! All the mistresses are little girls!