Genryusai stands as a founding elder of the World Ninja Association (WNA) and a legendary ninja. Despite his status, he exhibits a calm, laid-back demeanor in daily life. He is the twin brother of Genunsai, possessing a quieter, more reserved personality than his sibling.

Currently, he trains young ninja students to investigate extraterrestrial threats called Space Ninjas. His mentorship includes guiding Van after Van's father's injury in a housefire, instructing him in ninjutsu while supporting his parallel vigilante actions against Space Ninja incursions. Genryusai also accepts Kappei as a student upon Kappei's arrival in Komerica; sent by Genunsai specifically for training under Genryusai and to protect the gum-like alien Gumchi.

Within the WNA Academy, he mentors Burton and others, providing guidance through their challenges. His instruction emphasizes patience, notably demonstrated during Van's confrontations with Space Ninjas in the story mode. While his documented role centers on training and strategic leadership against external threats, further personal history or character development across extended media remains unspecified.