On a snowy school day like any other, classmates and childhood friends Hiroshi and Mizuki arrive at school to find the campus eerily empty. Before long, they find themselves trapped inside with six other friends, and even stranger, all the clocks have stopped at a very specific moment—the exact time when a former classmate jumped off the school roof to their death three months earlier. It turns out that this departed friend is their way out of their current predicament and may even be among their group…but no one can remember who it was that took their life on that sad day. The students must face themselves and their past memories to piece together the identity of this suicide victim or risk a similar fate-with their lives lost and forgotten inside these frigid school walls.