What was meant to be a pleasant seaside getaway in Okinawa turns into a nightmare for college student Kaori Sawahara when an unseen threat rises from the ocean. An odd device has given sea creatures legs, forcing them onto land to assault everything in their path. Kaori and her companions—passionate Erika and quiet Aki—are swept into the chaos, intensified by the foul odor of decay that clings to the beasts.
After braving the initial onslaught, Kaori attempts to reach her betrothed Tadashi in Tokyo. The line drops amid what appears to be another aquatic ambush. Worried for his well‑being, Kaori heads back to the city. While Erika and Aki battle the intruders in Okinawa, Kaori races toward Tadashi, unaware that the calamity is only beginning.