Gaito  

Gackto, Gakuto, 楽斗/ガクト

The leader of sea monsters who seeks dominance over marine life. He's commonly portrayed drinking wine and wearing black. His resemblance to Kaito caused Rina some initial displeasure. In anime, he is called Gaito (ガイト). Though there isn't a clear explanation for the name change, it could be due to distinguishing him from J-Pop star Gackt, whose name sounds similar in katakana. To emphasize this comparison, his name was spelled differently in the Del Rey manga translation as Gackto.