The Omid Islands are a maritime federation composed of twelve islands. Each island controls a kind of "tidal power" - some are wars, some are commerce, some are oracles, and some are poison arts. On the Twelve Islands, there is an empty position of "Tide Emperor". No one has sat on it for three hundred years because everyone who sat on it has died. Heroine: Su Yuan (she entered the island under a pseudonym, and her true identity was the destroyed Thirteenth Island. After that island was wiped out of history by the other twelve islands) Male Protagonist: Olan (the owner of the first island, a ruthless realist on the surface, but actually the descendant of the biggest beneficiary of the island annihilation incident three hundred years ago - and the person who most wants to find out the truth)