In place of Ratman who cancelled at the last minute, Mana joins Kitaro and the others on their trip. They`re headed to an inn exclusive to youkai - the Immortal Onsen. Everyone`s getting the most out of the hot springs, but suddenly, the inn is wrapped in an unsettling noise. The source is underground, the riotous energy from Mt. Fuji. Appeasing it is the job of the owner of the inn, but the current proprietress, Nebutori, is so fat she can`t always do her work. Mana offers to serve in her place. Mana and Kitaro go into the caves of Mt. Fuji, and a huge shadow closes in on them...!?