AD 2019: the giant mecha known as LINEBARREL falls to Earth, grabbing the attention of the anti-machina organization JUDA. Before JUDA can arrive on the scene, an unfortunate accident occurs: LINEBARREL crashes into Kouichi Hayase, a weak and frail pushover of a boy. Waking up underneath a beautiful naked woman, Kouichi discovers that he now possesses great power and can summon LINEBARREL for his own purposes. All Kouichi has wanted is to become a hero of justice and hold his own, instead his childhood friends Yajima and Risako fighting his battles for him – and now he finally has that chance. With LINEBARREL's power, Kouichi becomes cocky and aggressive, lashing out at those he cares about most; and as a 'hero of justice', Kouichi must find his new place in the world and protect himself from two organizations who want their hands on LINEBARREL.