JoelleAu
Princess Kohaku of the Spirit World, daughter of King Enma and the older sister of Koenma, the ruler of the Spirit World.
She who can very well become the Queen of the Demon World along with the three Upper S-Class demons, but she refused.
Lady Kohaku they address her, as the creator of Grim Reapers, as the only one who can bring judgement to demons after death.
The ruler of Nether World where demons go to after death, but she has long abandoned that title to her trusted man.
"I'm not a ruler, neither am I a fighter.. I'm the judge of life."
DISCLAIMER: I do not own Yu Yu Hakusho, the general idea and the characters except Lady Kohaku and her abilities as well as the idea of life after death for demons. The plots which were not included in the anime are mine as well. Similar scenes with the manga is purely coincidental, I watch the anime instead of reading the manga.