Pure x Holic: Junketsu Otome to Kon`in Kankei!? - Season 1

Taichi Amano, the main character, carries within him the "Awakening Mana." Through intercourse with a number of demi-women, this power of his undergoes evolution, and as a result he is selected to serve as the marriage and procreation partner for three of the foremost demi-humans: Hathor of the Divine Bull Tribe, Astraea of the Fairy Tribe, and Arle of the Holy Unicorn Tribe. Beyond that, it appears that by racial trait, once he takes a spouse he ceases to hold romantic feeling for anyone else. The three women grow ever more sexually forward with him, and so commences an unprecedented, fierce, and carnal contest over the protagonist.