The deep-sea mermaid clan believes that removing the tail bone spurs allows them to grow legs and come ashore. Sira, a mermaid born with zero bone spurs, is sent to land, only to discover that the so-called Ascension is a conspiracy by wealthy conglomerates. She barely escapes back to the deep sea but is not believed by her clan, and forms an alliance with Marlow, who is secretly investigating. The two gather evidence, expose the scam of Chief Kael colluding with humans at the grand ceremony, Kael the Shark is arrested by Marine Law Enforcement, the mermaid clan abandons their false delusions, and guards their own deep-sea homeland.
