In Japanese mythology, the tide jewels-- individually, the kanju (撟脩??, lit. '(tide-)ebbing jewel') and manju (皞????, lit. '(tide-)flowing jewel')-- were magical gems that the Sea God used to control the tides. Classical Japanese history texts record an ancient myth that the ocean kami Watatsumi 瘚瑞? 'sea god' or Ry贖jin 樴??? 'dragon god' presented the kanju and manju to his demigod son-in-law Hoori, and a later legend that Empress Jing贖 used the tide jewels to conquer Korea.

The fable of Tamatori-hime ????憪?'Princess Jewel Taker', which was a favorite ukiyo-e subject of Utagawa Kuniyoshi, is a variation of the Hoori and Toyatama-hime love story. Tamatori was supposedly an ama diver who married Fujiwara no Fuhito and recovered a precious jewel that the Sea God stole.