The story takes place during a fictional future, in the year 3567. During this time, a supernatural barrier called the Olynssis barrier, which disrupts space and time, envelops all of Earth. The planet is also being overrun by organic machines called Gardeners, which seek to exterminate all humans in order to "save and preserve" the planet. Tokito Aizawa is part of a group of hunters who destroys Gardeners and sells the scraps. Although, after encountering a girl named Tea, who constantly calls him "Koichi", and her giant machine, Silver, his life becomes more complicated.