Gin-iro no Olynssis

In the year 3567, the human race has lost their once technologically-advanced world due to their negligence with the planet. Now, their lives are in jeopardy when machines known as Gardeners are sent from the moon to destroy all mankind. Tokito Aizawa is a hunter who makes a living by destroying Gardeners and selling them for parts, but his life otherwise is fairly normal – until now. One day, while in town, Tokito meets a mysterious girl named Tea who calls him by the name "Koichi"; and in the midst of confusion, a large group of Gardeners suddenly attack the city. Tea then grants an unseen type of machine called "Silver" to Tokito – a machine that might be mankind’s best hope of evading destruction...