The old Genkai first comes to Yusuke's attention in his second Spirit Detective case, in which he was to stop a demon named Rando from learning Genkai's Reikou Hadouken fighting style. Genkai was holding a torunament because of her old age, and the knowledge of her techniques were to go to the winner. After a bit of a bumbling ordeal, Yusuke managed to defeat Rando and become Genkai's pupil. It was the beginning of a very tempestuous teacher-student relationship. They constantly trash talk each other, and Genkai will frequently beat up or otherwise humble Yusuke, but deep down Yusuke respects Genkai and Genkai recognizes the untapped potential in the Spirit Detective...and the fact that it takes just the right situation to coax it out of him. It's from Genkai that Yusuke enhances his Spirit Gun and learns the Shotgun technique, among others.

Genkai re-emerges during the Dark Tournament, first by training Yusuke for an additional three months. Then, a mysterious masked fighter emerges to fill out Yusuke's team of fighters. Yusuke assumes from the stature and size that it's Genkai, but a brief glimpse under the mask during a melee with Dr. Ichigaki's team throws the initial assumption for a loop. Under the mask, the fighter looked young and rather attractive.

But in the late stages of the tournament, Genkai reveals herself to Yusuke and reveals the secret of that change in appearance. When one exerts his or her spiritual utmost, the body changes to accomodate, and Genkai's prime was when she was in her twenties (that's the lady we saw earlier). She joined the team because the Dark Tournament is the perfect venue for Yusuke to fully mature his spiritual powers and reach his own peak. It happened already during the tournament when a dire situation made Yusuke attempt Genkai's ultimate attack, the Spirit Wave (and he pulled it off, too). She really didn't want to enter. She'd been there once before, even won it back when she was partnered with Toguro (the same Toguro who practically forced Yusuke to enter the current tournament). The two of them have a history, which makes the last phase of the Dark Tournament all the more interesting.

Genkai will entrust Yusuke with the sum of her spiritual energy. From here out, Genkai will rely on what little energy she has left...as well as any she can tap from her opponents. Without the energy for her Spirit Wave techniques, she falls back on another batch of techniques known as Spirit Reflection, which rely on synchronizing with the enemy's spirit energy and tapping into it, using it against them. So even without the bulk of her power, she ensures Team Urameshi's entry into the finals, using Spirit Reflection to defeat Shishiwakamaru and good-old-fashioned martial arts to down Suzuka. But she knew that she wouldn't be in the finals herself. This is because she had to face the Younger Toguro, her close friend turned bitter enemy, before the finals began. And without her spirit energy, it was no contest. Yusuke tries to intervene, but is only there in time for Genkai to die in his arms.

But Genkai gets a new chance at life when Team Urameshi wins the Dark Tournament. They wish for Genkai to return to the world of the living. This will have a strange influence on Yusuke and company, however. Because with the upcoming Makai Tournament, Genkai will train a number of fighters from the Dark Tournament. They, in turn, will enter the Makai Tournament…as rivals.