Genkai
Genkai is a legendary master of Spirit powers. She has a dojo on top of a moutain and she held a competition to select a student. Yusuke won it of course and trained with her for a couple months, then became a lot more powerful. Genkai appears to be a shrinked, dried, and old woman who easily get on your nerves. But actually, she was a very pretty girl when she was young. When Genkai releases all of her power she can for an instant turn back to her young. When she was young, Genkai trained under the same master as the younger/bigger Toguro brother, and apparently they had a kinda relationship. But then Toguro sold his soul to some youkai and became one himself, that's why he looks the same but Genkai's much older. Genkai was killed by Toguro as well, but outside the tournament, after she's given all her energy to Yusuke. Genkai waited for Toguro in the Spirit world , but he chose to go to the darkest deepest hell for endless suffering for some reason(possibly because he was still looking for challenges?) After Genkai died, Botan made another Genkai, but it's only a doll, it has her young looks and her powers, but no emotions.