You? How!? (A Rinharu Mermaid!Soulmate!AU)

The Shark Clan and Dolphin Tribe. They are both tyrants of the sea, but they hate each other. In the Clan and Tribe, and among outsiders, it is known that on everyone's 18th birthday, their soulmate's name will appear on their wrist. However, it is impossible to have a soulmate that is your enemy.

.. Or so everyone said, until the 18th birthday of the princes of the sea, Haruka Nanase, and Rin Matsuoka.

[I don't own Free! or any of it's characters!]