Fifteen years ago, the pilot of the S-class mech "Avenger" led three mechs in a suicide tactic to repel the giant beast "Kraken." The entire squad was wiped out, and he died in the line of duty. Fifteen years later, he lives under a hidden identity, working as a D-class mechanic at the Seventh Repair Station in Green Vine City, regarded by everyone as trash—including his own biological son, who has risen to become a B-class commander. But when an A-class leader of the Dark Star Legion bursts from underground, leaving his son's life hanging by a thread, he pilots that scrapped mech he has spent fifteen years repairing and, in front of his son, cuts down the powerful enemy in three moves. Everyone in the command center who once mocked him is left speechless with shock. And the crueler truth is this—the "Three-in-One Core," forged from the core energy of his three fallen comrades, can only sustain three moves.
