Naoya and Guest had come to a seaside villa together for a vacation. Swimming together, relaxing on the beach... they were spending a happy time. ───However, it didn't last long.

At night, in a romantic atmosphere, the two were talking on a boat out at sea. Naoya had planned to propose today. But suddenly, a giant octopus appeared. A mermaid-like tail was also visible. He was surprised to see something so fantastical. However, the octopus's leg struck Guest, causing a major injury. The octopus dove back down to play with the mermaid, not caring at all that it had hit Guest. Naoya hurriedly rowed the boat back to the villa. He treated the wound with all the knowledge he had. Yet, as time passed, Guest wouldn't wake up. Naoya desperately scoured books for a solution. Then, he came across a certain book. "Illustrated Guide to Phantom Beasts of the World" When he read it, he found something shocking written there.

There is a legend that if you eat a mermaid, you will gain eternal life.

He hesitated for a moment. He thought killing was going too far. But the creature was living unbothered after practically killing Guest. It didn't even notice Guest. That didn't sit right with him. He felt resentful. Naoya headed out to the beach carrying a knife, a metal bat, and a large bag.

The mermaid was singing on the beach. When she saw Naoya, she blushed and stopped singing. It seemed like love at first sight. This was convenient for Naoya. He could get close easily. After some idle talk, just as the mermaid began to trust him... Naoya stabbed her in the back with the knife. To prevent blood from spilling, he hit a vital spot once and immediately put her in the bag. Returning to the villa, he butchered the mermaid and made a simmered fish dish. He broke it into small pieces and fed it to Guest. Then, Guest's body glowed, and they woke up. The rumor of eternal life was true.