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 tournament 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 accommodate, 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.
Powers and Abilities
As Genkai herself puts it "Ive put myself through hell to make my body strong enough to handle my Spirit Wave orb" Genkai is a renouned human psychic and martial arts master. Her style called the Spirit Wave refers to two separate special moves and her personal hand to hand combat style. Even in her old age and without her orb she can hold her own with B-Class Demons as see when she battle Younger Toguro while he was using 80% of his power. Genkai has a profound understanding of how the Spirit World works and knows of demon world. conversely her name is known to almost every apparition and has been hunted for turning down a wish at the previous Dark Tournament.
Kiai Cannon: Genkai summons an invisible barrier of spirit energy that sned sanybody she wants flying back with a lot of force.
Spirit Gun: Like Yusuke, Genkai knows how to fire the Spirit Gun from her index finger by focusing her energy into the finger.
Spirit Shotgun: Genkai taught this move to Yusuke, She charges her fist with spirit energy and fires a large number of small blasts with a large spread. Useful against multiple weak enemies.
Spirit Wave Purification: A chanting move where Genkai stabs her energy into an opponent to cure them of various illnesses and possessions. This only works if the opponent is naturally good, if evil this move destroys them.
Spirit Wave Orb: An orb comprised of Spirit energy compressed into the smallest space. Her training allowed her to create this and is the way she passes on her style by giving Yusuke this orb.
Spirit Reflection Blasts: Genkai locks on to the spiritual wavelength of her opponent and steals a portion of that energy using it to fuel a blast.
Spirit Cuffs: A training m,ove that makes the target need to use 100% muscle and 100% spirit energy all the time to even walk. Genkai used this on Yusuke to help him prepare for Younger Toguro.
Spirit Healing: Genkai uses her energy to heal someone. This can even heal broken bones.
Paralyzing Touch: Genkai can paralyze an opponent with a simple touch.
Spirit Barrier: Genkai can summon a barrier of energy to block attacks.
Soul Return: Genkai can manipulate souls and return them to their original body.
Spirit Wave: Genkai's signiture move where she uses her entire body as a focal point for her spirit energy. This causes her to revert to her 20 year old self as a side effect while she is fighting.