High schoolers Mizuho and Wataru are going on a kendo club trip, but because nobody apart from them can go, Wataru decides to invite his younger twin brother Kakeru as well. He decides to go with a woman called Ayumi who is in love with him.

Once they arrive at the hotel, they discover a virus inside of it. To make matters worse, the hotel keeper Kamishiro-san and his ten year old daughter Koyuki both have it and are insane, but they can't leave because there is a big snow storm outside...