Muv-Luv Alternative

On April 19th, 1973, a race of extra-terrestrial lifeforms launched a landing unit from the moon, which touched down on Earth, in central Asia. Ever since, mankind has been engaged in a losing war against this alien species, known as the BETA, as they have gradually expanded outwards across the globe. After 20 years of non-stop fighting, the war has reached the shores of Japan...

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?

As Takeru starts to feel anxious about whether or not he can actually make a difference, Professor Kouzuki demands more concrete evidence of his knowledge about future events.