It has been 12 years since Kyon made his fateful decision to leave the world of The Disappearance of Haruhi Suzumiya. Kyon and Haruhi are now raising a family. One day Kyon's young female counterpart suddenly appears on their doorstep, the sole survivor of an armageddon that has destroyed her world. Kyonko is alone. Kyon then helps her with a crisis that could end the multiverse.