In 2140 AD, core energy exhausted, the surface reduced to radiation wasteland, humanity migrated to underground "Abyss City". Energy monopoly giant "Titan Heavy Industries" controlled everything. Once an ace mecha pilot youth "Chiyan", due to an accident was stripped of qualification, reduced to a bottom-layer mecha scavenger. One day, deep in the wasteland he accidentally awakened a sleeping hundred-year-old ancient mecha "Dawn". To protect his sister and partners, Chiyan drove this mecha regarded as "scrap iron", launching a challenge against Titan Heavy Industries' rule.