Zetter combine with his support rescue robot Double Nine to form Zetter 99 then combine with his brother Gunber 01 and Father's remaining support machines to form Zetter Gunber.

Zetter transforms into a Mercedes-Benz ML270 CDI fire car. He's son of Father and Gunber's oldest brother. He's has a more calmed personality than Gunber and loves to play soccer.

During a small baseball game with the protagonist, Gunber's homerun accidentally broke the Orb of Protection that kept the ancient Demon Jerkin trapped within.

He gets kidnapped along side with the unselected protagonist avatar by the Demon Jerkin.