Following on from the events of List of The Melancholy of Haruhi Suzumiya episodes, the story takes place from December 16 until December 24, a month after the Japanese Cultural Festival. The SOS Brigade, led by Haruhi Suzumiya (character), makes plans to have a nabemono party for Christmas. However, on the morning of December 18, Kyon arrives at school and finds that the very nature of his reality has changed; Haruhi and Itsuki Koizumi are missing, Ryoko Asakura has mysteriously returned, Mikuru Asahina does not recognize him and Yuki Nagato is an ordinary human. Only Kyon is aware that everything is different and no one else remembers anything about Haruhi or the SOS Brigade. The only clue Kyon manages to find is a bookmark left by the alien version of Yuki before everything was changed, telling him to gather "keys" to run a program. While wondering about this clue, he gets to know the new Yuki, who appears to be quite fond of him. As December 20 comes, Kyon learns from List of Haruhi Suzumiya characters#Taniguchi that Haruhi was at another high school the whole time, along with Itsuki and others formerly from his school. By revealing his identity to her as 'John Smith', an alias he had used when he travelled back in time to assist a young Haruhi, Kyon manages to convince Haruhi to believe his story. With her assistance they gather the SOS Brigade together in the club room, thus bringing the keys necessary for a program built by alien Yuki.