Toki is a practitioner of Hokuto Shinken, a lethal martial art that allows its wielder to destroy an opponent from within, who was trained alongside Kenshiro. Traditionally, the art is only passed from its official master to a single student, but if the master takes on multiple students then they are obliged to give up the art when a successor is chosen amongst them. Toki stood as the most likely candidate to become the next master, however he came down with a terminal illness and thus Kenshiro inherited the position instead.
Afterwards, Toki chose to spend his remaining days traveling the world and using the healing arts of Hokuto Shinken to treat the sick.
Despite his illness, Toki is still an incredibly formidable martial artist who few could defeat. and possesses great insight and clarity of mind. He shares strong bonds with Kenshiro, who sees him as a mentor, and Raoh, Toki's biological brother.