A young, black-haired, male human midshipman serving aboard the exploration vessel Streaker, Toshio hales from the water world Calafia, where humans and neo-dolphins live in harmony. Toshio is recruited to help with dolphins' artificial-hand/eye coordination. He receives a variety of nicknames throughout the novel, including "Little Hands," "Great Dreamer," "Ladder-Runner," "Sharp-eyes," and "Shark-biter." Toshio's best friend is Akki, a midshipfin. Toshio speaks the neo-dolphin language Trinary badly.