She trains Yusuke in the Spirit Light Wave Fist (Reikou Hadou Ken), known as the Spirit Wave in the English dub, pushing him to his limits. Though she may seem harsh towards Yusuke and the others, she genuinely cares for all of them and strives to guide them on the right path.
Genkai is an elderly martial arts master who resides alone in a large temple. She first appears during Yusuke's second case when he infiltrates a tournament she is hosting to find a successor for her techniques and locate the demon Rando. Genkai is a legendary reiki master, renowned in both the human and demon realms. Yusuke wins the tournament, defeating Rando, and becomes Genkai's student.
When she was 50 years younger, Genkai and the younger Toguro brother were lovers and teammates in an earlier Dark Tournament. After their victory, Toguro chooses to become a demon, while Genkai returns to the human world, causing a rift in their relationship. She enters the next Dark Tournament with Yusuke, disguised as the "Masked Fighter," to confront Toguro once again. Her signature technique is the Spirit Wave, which channels spirit energy from the entire body and can be directed through various forms. This makes her technique effective for healing, purification, and combat. A side effect of using this power is a temporary cellular shift, allowing the wielder to briefly revert to their most powerful form. For Genkai, it allows her to regain her youth temporarily.
Despite her advanced age and diminished physical and spiritual strength, Genkai remains a formidable fighter. Even after transferring most of her power to Yusuke, she still retains some Reiki abilities, notably during the Chapter Black saga.
She dies fighting Toguro.
