A sudden meteorite wipes out an entire city from the map and the main character and her friends who were otakus in their thirties realize they've now reincarnated into high school girls.
Main protagonist, Yudai Morimura [a.k.a. "Morrison"], appears in Shibuya with a grand plan to accumulate wins at high-rate free games...
It has been a year since the human race was destroyed by an unknown virus that suddenly spread, and three high school girls, Harumi Koharu, Tsukishima Natsuki, and Akechi Chiaki, have been spending their time at school playing games that they could not do before they were born. But then, Koharu finds a butterfly with a plant growing out of a flower bud, and even dogs, cats, and other creatures are growing plants... What on earth has happened to the Earth after the spread of the virus? (Source: Takeshobo, translated)