The Tokyo Bay Aqua Tunnel is suddenly collapses as it's inundated with water. At the office of Prime Minister Okochi, the cabinet is assembled for an emergency conference. Among all the opinions about the catastrophe being caused by an earthquake or a submarine volcano, only the Deputy Chief Cabinet Secretary, Rando Yaguchi, points to the possibility of it being the work of a giant sea creature. While the other cabinet members laugh off Yaguchi's opinion, but they're forced to confront the reality when the mysterious giant creature emerges from the sea and enters urban Tokyo......