Bakemono no Hanayome
Uke is a ‘freak’ fox who has nine tails and is being married off to the second born of the leader of wolves. Uke was tasked to kill him to cause chaos but he failed and after the wolf (seme) pounced on him and de cleared him his wife he was chained and seme stayed with him. Seme didn’t touch Uke other and feeding and washing. Seme eventually left him out of chains and Uke started to fall for him. Seme took Uke to see the sun rise over the ocean and they both realized something. Seme decided to let Uke be free and left him. Uke found his way back eventually and was lead to where seme was and found a werewolf. Seme transforms into this monster every full moon. Seme escaped him cage and attacked Uke but Uke accepted it. Once Uke awoke they both realized their feelings and reciprocated them happily. They ran away together and ran into humans and semes mother. They started a new life with them and are happily still married.
Mermaid's Egg