Suzumiya Haruhi no Shoushitsu

In mid-December, Kyon and the other members of the SOS Brigade are preparing for the Christmas party Haruhi Suzumiya has planned. Only days later, Kyon arrives at school to find reality completely altered: Haruhi and Itsuki Koizumi are missing, Mikuru Asahina has never met him, Yuki Nagato is an ordinary shy girl, and Ryouko Asakura has returned to class as though nothing ever happened.

Kyon is the only person who remembers the previous world, and almost no evidence remains that the SOS Brigade ever existed. As he searches for the cause and a route back to the reality he knew, he receives a choice he never expected to have: accept a quiet world without aliens, time travelers, and the supernatural disturbances he complained about for so long, or risk everything to restore the chaos and the people he realizes too late he does not want to lose.