Adopted and raised by Ryuuken alongside Kenshiro, Raoh and Jagi as a potential successor to Hokuto Shinken, Toki proved the most promising candidate, being far more skilled than Kenshiro and Jagi, and a much more ethical and perceptive student than Raoh. However, Toki lost his place as the successor when he was irradiated by the nuclear fallout. Though he survived thanks to his superhuman constitution he was left terminally ill and thus unsuitable to inherit Hokuto Shinken's mantle, which passed to Kenshiro instead. Toki decided to use what time he had left to travel and use the secrets of Hokuto Shinken to heal the sick.
Toki possesses a serene disposition, great insight, and despite the weakness brought on by his illness, prodigious ability as a warrior, to the extent that while Raoh considered Kenshiro an insignificant threat, he still viewed Toki as a genuine danger. Although the three brothers all use Hokuto Shinken, there are fundamental differences in their application of the art, Toki specliaising in a "flowing" style which allows him to move in perfect tandem with an opponent's movements and practicing the "Gentle Fist" which causes the people he kills to feel euphoria rather than pain as they die.
Toki shares strong bonds with Kenshiro, who admires him, and Raoh, who is both Toki's genetic brother and childhood idol. Alike Kenshiro, Raoh, Jagi, Shin & Jyuuza, Toki was also in love with Yuria, but unlike most of the others, he never attempted to court her. Toki also has a further two genetic sibling, Kaioh and Sayaka, though they never appear together in the series.