Genkai is one of the best characters on the show.
We first learned of her early on in the series as she’s an aging martial arts master looking to pass her secret technique to a successor before she dies.
Most of the applicants thought her goofy games were dumb, but they were secretly measuring their spirit power.
And Yusuke wins her tournament, but with some luck.
Which he initially regrets, as her training is very brutal.
She joins her apprentice and his friends for the Dark Tournament, hiding under the name Masked Fighter.
We really only get to see her use the Spirit Wave at full power once. And it was used to heal, instead of to hurt.
Even after giving her apprentice the majority of her power, she was still able to defeat demons of incredible strength.
This fight made me laugh out loud.
What didn’t make me laugh, was her fight with Toguro.
Turns out they were lovers over half a century before. But they broke up after he wanted to become a demon.
And he brutally murdered her.
Turns out that even he planned for her death to be temporary. But they had their goodbyes in spirit world.
Her role is rather limited in the last two sagas. She was pretty essential in the fight against Sensui.
In the last saga, she trains some of the Dark Tournament demons to fight for Yomi as a favor to Kurama. I don’t think she dies in the anime, but I know she passes away of old age in the manga.