Mt. Horai (or Ryugu-jo Castle) where Urashima Taro stayed, was a legendary mountain on which sennin (immortal mountain wizards) lived, and behind the story were concepts concerning Taoist immortality in which eternal youth and immortality were prized in ancient China.
浦島太郎がいた蓬莱山（竜宮城）とは仙人が住むという伝説の山であり、古代中国の不老不死を願う神仙思想が背景にあった。