Gaito

The leader of the sea monsters who is bent on taking over the marine world. He is always depicted drinking wine, and wearing black. His resemblance to Kaito made the latter a subject of initial ire by Rina.

He is known in the anime as Gaito (ガイト). There is no official reason for the name change, but one obvious reason is to distinguish him from the J-Pop star Gackt, whose name is spelt the same way in katakana.