Based on a shounen manga written by Shimizu Eiichi and illustrated by Shimoguchi Tomohiro, serialised in Champion RED.

Kouichi Hayase was involved in an accident and falls into a coma for half a year. Due to this accident he becomes depressed and lonely. However, unbeknownst to him he attained a great power and three years later a giant robot (Linebarrel), which was the cause for the incident, appears before him, causing Kouichi`s life to change.

(from AniDB)