There are also some Raen among the Malaguld Xaela tribe (notable for being the only Xaela tribe willing to accept Raen among their number). Of course, these Raen tend to be exiles, so they COULD have originated from Sui-no-Sato.
Still, as others have noted, Sui-no-Sato is likely NOT the only home to Raen. Yugiri's leaving the underwater settlement was noted to be an unusual thing - and yet there are many, many Raen to be found in places like Kugane, and they're scattered here and there in other places, as well - even Eorzea has a few. This seems like far too many to have all originated in that same underwater town.