During what was meant to be a tranquil beach getaway in Okinawa, Kaori Sawahara, a college student, faces a nightmarish scenario as a terrifying threat emerges from the sea depths. An eerie contraption seizes control of marine life, giving them legs to wreak havoc on land. With her companions Erika and Aki by her side, Kaori battles the reeking undead creatures. After a harrowing ordeal, Kaori attempts to reach her fiancé Tadashi in Tokyo, only to be interrupted by a disturbing incident hinting at further fishy assaults. Worried for Tadashi's safety, Kaori embarks on a journey to Tokyo, unaware of the escalating crisis. Meanwhile, Erika and Aki grapple with the ongoing attacks back in Okinawa, setting the stage for a series of unforeseen events.