On February 11, the group heads to the mountains for a two-day skiing trip to make some memories before Yu returns home the following month. As the group spends the day skiing and snowboarding, Yu gets the feeling he is forgetting something important, which becomes more apparent when the group looks over photos and videos from the past year and notice something does not add up. Upon realizing that there was somebody alongside them that they have somehow forgotten about, Yu and the others decide they should investigate once they return home...