At the northern end of Hokkaido, there's a vast and dense forest that covers a thousand mile radius that is completely isolated from human civilization. The regular temperature is lower than the arctic circle and in a day, this can reach as low as -40 F.
To get away from the city, an avian professor and a team of researchers travel deep into a cabin located in the middle of this forest to spend a couple of weeks in the new year season.
Two poachers suddenly get attacked by a gigantic 800 lb brown bear, strong enough to shatter a lion's neck with a single bite. The animal population was declining in that area and it was a common belief that poachers were to blame. But a dark legend from that area indicates that a gigantic beast called "Shatoun" (the sleepless one) doesn't hibernate and has decimated the population of brown bears and humans in the area, constantly attacking and devouring creatures in his path.
Eventually, Shatoun causes havoc in the cabin where the humans are devoured one after another. Isolated and cut-off from comunication with the world, it's up to Kaoru Tosa, a 29 year old frail TV reporter to escape alive with her 9 year old daughter from the fangs of this unstoppable and bloodthirsty beast!!