Shirogane Takeru found himself inexplicably transported to a world that resembled his own in many ways, with one major difference: For nearly 30 years, mankind has been at war with the alien BETA, who have succeeded at wiping out over half of humanity and had nearly captured the entire Eurasian continent. As Takeru tried to come to grips with this bizarre new reality, he realized too late that the majority of humanity will be abandoned with the Earth, as the chosen few escape to the stars, hoping to find sanctuary.

Now, equally inexplicable reasons, he finds himself returned to the first day of his time in this alternate world. Will the experiences and knowledge he has gained allow him to make a difference?
And it happens on December 24th?
وسيحدث هذا يوم 24 من ديسمبر؟
Und das ist dieses Jahr
am 24. Dezember passiert?
¿Y dices que ocurre el 24 de diciembre?
¿Y dices que ocurre el 24 de diciembre?
Il sera donc lancé
le 24 décembre de cette année…
E cosa è successo il 24 dicembre?
E isso acontece em
24 de dezembro deste ano?
Это случится двадцать четвёртого
 декабря текущего года?