Muv-Luv

Muv-Luv Extra, is a typical high school visual novel, but the second part Muv-Luv Unlimited starts with Takeru Shirogane waking up in his bed, reminiscent of the start of Muv-Luv Extra; however, Takeru quickly realizes that neither Meiya nor Sumika come to wake him that morning. Upon leaving his house, he finds his neighborhood destroyed and Sumika's house crushed under the wreckage of a large mecha. Takeru later learns that he is in an alternate world to Extra. (wikipedia.org).