Rebirth of Armed Mecha

The accidental death time travels to the young boy Koichi who is seriously injured and on the verge of death. When he woke up leisurely, his body gained unprecedented power... He was originally weak and timid, but became a completely different person after his soul possessed him. However, just three years after the incident ended, the super-large robot "Line Barrel" that caused the accident appeared in front of Koichi!! What does this mean? This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.