Yubei, a stunt actress, accidentally fell into the sea into the territory of the mersharks, the enemy of humans. To survive, she bluffed that she was a human princess. In order to meet the human emperor and negotiate for a ban on the slaughtering of ocean life, the mershark prince who has been cut off from communications with the land dwellers for hundreds of years held a sensational underwater "marriage" with the "human princess" Yu Bei. However, the prince never expected that after following Yubei on land and into the drastically changed human world, he would fall into a scam that she reluctantly arranged to take his teardrops so that she can save her father —— And so commences a chaotic historical princess theatrical drama...