I finished reading most of the MuvLuv manga series, Muvluv, Muvluv Unlimited and Alternate (mostly).
Essentially, its very different from what I've seen of the anime.
Manga is based on started as a love triangle/our main male characters, a childhood friend and heiress. It's normal school comedy essentially, until in Unlimited he wakes up in alternate universe. Outside of his intact room and ruined house is that the city of Yokahama is in ruins. Everyone he knows doesn't know him. One of his friend doppelganger is a girl instead of a boy. His class mates are all soldiers cadets to fight invasion by the Beta (Barbaric Extra Terrestrial Aliens). Our young hero isn't soldier, but he manages to convince his teacher who instructor at let him join this training base and that he is from another universe. In the original world, she is infact a scientist who was taking a break and was doing teacher gig. Here she scientist / instructor and just as crazy/smart.
Essentially, the story goes on main character life on this alternate world, trying make due since he isn't sure he could back. Basically he tries help out where he can. His life playing a video game mecha game gives him better hand coordination abilities his fellow cadets.
Muvluv Alternates is Ground Hog day. Our main character survives 3 years and dies with rest of humanity who was left behind by colonist effort save some people. His chosen wife survives with a child. However for some reason he returns to back where he started but he has 3 years of experiences and his physical body is combat able. He has to relive his time when he arrived from his old world, but begins alternate the course of events. He soon finds out, nature of his being in the past and possiblity to return to his original world and get key perhaps save humanity of this world.
Its alot better than anime, i didn't like the horror aspect of the BETA. Fan service is toned down in Alternate, but its more apparently in the earlier unlimited which is a self-contained story.
I didn't think i liked it, but it good.