Agito is living in the world 300 years after the present day. It is the world where the forest assaults human beings because of the failure of gene manipulation. However, there are people living strongly and happily. One day, Agito meets Tura, a girl from the past. She has a mission to revive civilization. In order to save her at the cost of his life, he contracts with the forest to obtain a forbidden power, and his hair turns grey.