Moito is the younger brother of Kei. The brothers live near the Spanish coast and endure the loss of their fisherman father, who died at sea. Before his death, their father gave Kei a whalebone-carved pan flute, forging a family link to the ocean.

Moito and Kei find an injured baby albino whale trapped by rocks in a shallow coastal inlet. Together, they conceal the whale in this secluded spot and undertake the task of nursing it back to health.

After the whale, named Peek, is discovered and captured by a circus owner, Moito joins Kei in attempts to free it from captivity. Both brothers share a motivation driven by empathy for the whale and the goal of returning it to the sea, with their actions presented as a unified effort rather than detailing Moito's individual role separately.

Moito's background and development are closely connected to his relationship with Kei and their shared experiences. The loss of their father and the subsequent discovery of the whale shape his part in the central rescue mission. His character operates within the sibling dynamic, reflecting themes of protection and empathy.