Traitor! The Enlarged Robot, Vikong!

"Traitor! The Enlarged Robot, Vikong!" it's the 12th episode of Mazinger Z. This episode first aired in Japan on February 18, 1973.

Summary
Baron Ashura is looking for his master when he spots Dr. Hell aiming a rifle at him. Thinking he's about to be killed as punishment for his various failures, Ashura begs for his life. After being shot, instead of being killed, he grows to giant size. Turns out the gun is Dr. Hell's new invention: the Giant Making Rifle.

Baron Ashura tries to take revenge for being mistreated, but Hell shoots him again before he's able to do anything. Hell brushes off the betrayal attempt. After explaining the gun still needs adjustments and testing, he gives Ashura the weapon and sends him off.

Koji's school is holding an event to celebrate its founding anniversary. During an exhibit beind held at the event, the gang meet Junichi. The boy's showing off Vikong, a remote controled robot he created. Junichi says the robot is like a little brother to him which prompts Boss to mock him. This starts a fight in which Vikong takes Boss down, Before he can retaliate, Sayaka intervenes and asks him to accept Vikong as the winner. Boss does so and leaves.

Meanwhile, Baron Ashura's search for a suitable target for the rifle isn't going well as he is unable to find anything that would pose a threat to Mazinger Z even if enlarged. That's when he hears some students talking about Vikong. Ashura sneaks into the school, attacks Junichi and steals the robot.

After equiping Vikong with weapons, Ashura uses the Giant Making Rifle to enlarge it. The former toy now turned into the Mechanical Beast Vikong O9 is sent to destroy the city. Mazinger Z and Aphrodite A sortie to stop the enemy robot.

Junichi begs his creation to stop attacking to no avail. Out of options, he tells Koji about Vikong O9's weak spot which results in Mazinger Z being able to destroy the Mechanical Beast.

Recurring

 * Koji Kabuto
 * Sayaka Yumi
 * Shiro Kabuto
 * Gennosuke Yumi
 * Dr. Hell
 * Baron Ashura
 * Boss
 * Nuke
 * Mucha

Debut

 * Junichi(Only Appearance)

Machines

 * Mazinger Z
 * Hover Pilder
 * Bicong 09
 * Aphrodite A

Weapons

 * Breast Fire
 * Rocket Punch
 * Koushiryoku Beam
 * Missile Punch (Debut)
 * Giant Making Rifle (Only Appearance)

Trivia

 * When talking to Junichi, Koji wonders if robots are able to understand humans as Mazinger Z's seems to move - in some part - accordingly to his thoughts. Although there's no explicit confirmation, is common for the robots to exhibit body language that mirrors their pilots' feelings or movements even when there would be no point for them to be made to do so.
 * One notable instance can be observed in Minerva X, The Mysterious Robot as Aphrodite A's shown moving in a way that mirrors Sayaka's when the later gets angry at Koji.
 * The episode seems to imply the Giant Making Rifle will play a part in later episodes. Although the weapon does not gets destroyed, it never appears again.