Where I Belong by tbmd1066
After being injured as a child, Haru, a merman, has been living in a marine facility. Fortunately, he befriended Makoto, the son of one of the scientists, who taught him how to communicate via sign language and helped make his life just a little easier. When another injured merman is brought to the facility, Makoto and Haru are faced with a new adventure.
This is a beautifully written story that has captured my heart. Due to Future Fish, most Free! fans already see Haru as a merman. There are plenty of merman stories out there, but this one is unique in that Haru has spent most of his life with humans at the facility. He's been able to forge a close bond with Makoto that's really sweet to watch.
Definitely give this delightful story a story!
artwork credit: Y-nY