Mermen were a race that inhabited the seas located around the Roble Holy Kingdom. They had a long history of mutual cooperation with that nation. However, the memories of war with demi-humans still remain strong with the humans and elevate the sentiment that they could never truly accept them as allies.
According to the Web Novel, Mermen were marine creatures.
- In the Web Novel, the Mermen are also found in the Argland Council State.
- One Merman, named Ran Tsu An Rin is a member of Nine Colors.