Mayu is the daughter of the brilliant engineer Tochiro Oyama and the legendary space queen Emeraldas. Orphaned or separated from both parents, she grows up on Earth under the protection of Captain Harlock, who becomes a father figure to her. She is often placed in a Christian boarding school on Earth, where she lives a quiet and sheltered life. Her most distinctive trait is her ocarina, whose simple melody serves as a beacon that Harlock can hear and follow, symbolizing the intangible bond between them. The Earth government, aware that Mayu is the only person whom Harlock genuinely cares for, frequently uses her as bait to lure him into traps. Despite this, Mayu remains gentle and resilient, embodying the innocent humanity that Harlock has sworn to protect. She deeply loves Harlock and repeatedly asks to join him aboard the Arcadia, but he honors her father Tochiro’s dying wish that she remain on Earth, away from the dangers of space piracy. In the story of Captain Harlock: Mystery of the Arcadia, Mayu’s role is central to Harlock’s motivation: her safety compels him to defend Earth even when the planet’s own leaders brand him a criminal. She also becomes the means through which the secret of the Arcadia’s main computer—which contains the spirit and consciousness of her father—is revealed to Harlock. Over the course of the narrative, Mayu’s emotional resilience is tested, but she never loses her trusting nature or her quiet hope, serving as the emotional heart of the conflict. She has no combat abilities or special powers, but her playing of the ocarina and her mere presence act as a moral anchor for the crew of the Arcadia.