Yuyuko Saigyouji is the head of Hakugyokurou in the Netherworld. She has been a ghost for over a thousand years, making her an exceptionally long-lived ghost. Although, perhaps "long-lived" isn't quite the right phrase...

Ghosts are spirits who can't pass on due to them not realizing they are dead or because they vehemently refuse to admit it. The difference between ghosts and phantoms is that ghosts retain the form they had when they were alive. Ghosts can also speak and interact with objects.

Seeing Yuyuko's ability to manipulate death, the Yama tasked her with managing the phantoms waiting to go to Nirvana or reincarnate. In return, Yuyuko was granted permanent residence in the Netherworld. Ordinarily, she only has phantoms to talk to, so when a human from the land of the living comes to visit, you might catch a glimpse of her playful side. She might abandon all her duties and chat the day away.

Yuyuko once found an ancient record in her bookcase, and supposedly, this is what caused her to instigate the Spring Snow Incident. It's unclear when the record was written, but having read it, Yuyuko concluded that someone would be revived if the seal on the youkai cherry blossom tree, the Saigyou Ayakashi, was broken. Out of mere curiosity, she began gathering spring but was stopped by a perceptive shrine maiden. This was for the best since, had the revival been successful, things would've surely spiraled out of control...

Reimu will surely take you to the Netherworld when spring comes around. There, you'll be treated to the beautiful sight of the cherry blossoms in full bloom, and you'll hear the cheerful voices of those attending Hakugyokurou's party and the performance of the Prismriver Ensemble. Then, Yuyuko will beckon you over with a wave as if she's been waiting there just for you.