I Became a Monster Girl and Drifted in Another World.

Newcomer + transformation + no system + slow warming + marriage change + self-created western fantasy worldview adventure, the protagonist changes from a human to a monster girl Age of the Creator The beginning of everything comes from a mysterious existence, which people only call "the Creator". He created those monster girls with extraordinary talents for the survival of humans in the world. These demi-humans are collectively called "Ishmuti" and include many completely different races. Each race is endowed with a specific mission in their physiology. Some Ishmutis are invincible warriors, masters of weapon making or spiritual spellcasters, others are born as ordinary workers and civilians; and some races are born to be leaders, disease carriers, secret keepers, priests, and powerful superiors. It is worth noting that all Ishmutis are female, a natural means of population control. Notice! The Ishmutis must rely on humans to reproduce! "So I have to give birth too?" "Yes." "Which race?" "All of them"