Tide jewels

In Japanese mythology, the two tide jewels, named hirutama/kanju (干珠, "[tide-]ebbing jewel") and mitsutama/manju (満珠, "[tide-]flowing jewel"), were magical gems that the Sea God used to control the tides.

The earliest texts record an ancient myth that the Sea Deity (海神, Watatsumi) presented the tide jewels to his son-in-law Hoori aka Yamasachihiko (Prince Luck-of-the-Mountain).

Later Japanese writings refers to the tide jewels as being in the possession of the Dragon God (龍神, Ryūjin) or Dragon King or being housed in his Dragon Palace (龍宮, Ryūgū), where the myth of the loan of these jewels became attached to the conquest of Korea by Empress Jingū.