Genkai is Yusuke's teacher. She taught him how to use the Spirit Wave, to better his powers, and improve his techniques.
Genkai competed in the Dark Tournament 50 years ago and was apart of the winning team. She wished to never be bothered with the committee again, but her apprentice, Urameshi was threatened and he had to enter or everyone he loved would be killed. Genkai entered as the fifth member of his team, calling herself the Masked Fighter. But she was killed by Toguro before the finals of the Dark Tournament. Toguro and Genkai had been on the same team in the previous tournament 50 years ago, supposedly they had been lovers. Toguro had wished to become the strongest demon and to never age, that ended their relationship. Genkai was brought back to life by Koenma once Yusuke and his team won the tournament.
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