Deep Blue (ディープ・ブルー Dīpu Burū) is the leader of the aliens. He came to Earth years before the others and assumed the form of a human boy, Masaya Aoyama, to avoid detection. Deep Blue went to sleep within his new body, leaving Masaya with no memories of who or what he really is, but retaining some of Deep Blue's disgust for the way humans were treating the environment. Despite being the primary antagonist, Deep Blue does not actually appear until the end of the sixth volume of the manga.
Deep Blue is cold natured, cruel hearted, and will kill anyone who gets in his way. Upon awakening, he attacks and injures Ichigo as he does not share Masaya's love for her, and kills Kish without any hesitation when challenged to a duel. This allows Masaya to temporarily re-emerge and release mew aqua inside his body, killing them both.
The anime adaptation shows Deep Blue as a voice coming from a blue light, to whom Kish gives progress reports, and a shadowed version of his true form is seen when Kish brings him some mew aqua in episode twenty-six. His death is changed in the anime to come at the hands of Mew Ichigo rather than Masaya, though Masaya aids her by taking over the body. To keep the true identity of Deep Blue a secret, his voice actor's name is shown only as a question mark until his identity is revealed in episode forty-nine; after which the credits are changed to list Megumi Ogata (who also voices Masaya and the Blue Knight). Deep Blue is one of the few characters whose name remains unchanged in the Mew Mew Power dub. The anime slightly modified his role from that of a savior for the aliens to a destructive force that wants to do nothing but destroy the Earth which causes the aliens to turn against him. In the Mew Mew Power English adaptation of the anime series, he is voiced by Scottie Ray.