The manga centers on Naomichi Kuga, a high school student who works at his family’s electronics repair shop. He embarks on his first school trip aboard a luxury ferry bound for a seaside resort, but the voyage takes a deadly turn when something massive collides with the ship. The collision allows a horde of mysterious man-eating monsters from the deep sea to board the vessel, and they begin hunting the passengers and crew.

Naomichi and his terrified classmates find themselves trapped in a desperate fight for survival. Forced to flee the sinking ship, they manage to reach a remote island, only to discover they are not safe from the creatures. Stranded far from home with no immediate hope of rescue, the group must learn to survive on the island while constantly evading the ravenous sea monsters that stalk them both in the water and on land. The story follows their struggle against the relentless predators as they wait for help that may never come.

The main protagonist is Naomichi Kuga, a young man balancing his high school life with his family business, who must find unexpected courage when disaster strikes. The story was written by Yuuki Fujisawa and illustrated by Yasunari Toda. The narrative is structured as a panic survival thriller, unfolding across a confined luxury ferry and later a deserted island, which heightens the sense of isolation and danger.

The narrative arc begins with the collision and the initial attack on the ferry, creating chaos as the characters first encounter the creatures. The middle section focuses on the escape to the island and the subsequent struggle to establish a safe haven while fending off the monsters. The story concludes with the final volume, which brings the survival story to its end.