Aoi Umi no Sashimi

Nagisa, a recent human-to-mermaid convert, is adjusting to life in the ocean when she collides with a research submarine, causing her to lose her memory and be taken aboard the Sogei. Osanai, her former human love interest who is also on the submarine, attempts to conceal his past relationship with her. Meanwhile, Nagisa’s mermaid companion, Tsunami, undertakes a mission to locate her. Tsunami aims to warn Nagisa that if she remains silent for an hour—due to her incomplete transformation—she will revert to human form and face a drastically reduced lifespan.