Its Too Soon to See Nirvana!

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)