Pure x Holic: Junketsu Otome to Kon`in Kankei!? The Animation

Taichi learns he can break the supernatural marriage law binding three demihuman leaders to him by using a Refusal Seal during intercourse. He first frees Hathor, the cow-girl, through repeated sexual encounters, and she promises to become his wife once he helps the others. Next, he visits Astraea, the elf, and successfully uses the seal to release her from the same racial constraints. By the end, both women have developed genuine feelings for him, leaving only Aruru still to be freed.