Rubangar King (ルバンガーキング Rubangā Kingu) was a Kaiju from Jumborg Ace that first appeared in episode 2. He was created by Anti Go-Ne.
Subtitle: Saber Monster (サーベル怪獣 Sāberu Kaijū)
- Height: 56 m
- Weight: 52,000 t
- Origin: Space to Ginza, Tokyo
The second monster that Jumborg Ace had face, Rubangar King was created after Anti Go-Ne shot his monster summon beam at a damaged Kaiju figure, transforming it into a kaiju. Rubangar King started rampaging in Ginza but PAT arrived and attacked the monster. Rubangar King fell down onto the ground, opened his back to reveal some cannons and started firing missiles. PAT struggled with the surprise attack, until Naoki came with his delivery cessna and transformed it into Jumborg Ace. Jumborg Ace fought Rubangar King and managed to prevent it from using it back missiles. Jumborg Ace then used his Beam Emerald on Rubangar King, but the silver fins on his head reflects the beam right back to Jumborg Ace's eyes, blinding him. PAT fortunately helps Jumborg Ace and shoots at Rubangar King, making him fall on his back this time. On seeing this, Anti Go-Ne fired a beam from his ship, causing Rubangar King to teleport away.
Later in the episode, Anti Go-Ne releases Rubangar King again to destroy more of the city. PAT tries electrocuting it using wires, but it instead causes the saber on his top head to fall off. Rubangar King uses the saber to cut off the wires. Naoki, however, recovers from his blindness and turns his plane into Jumborg Ace again. Jumborg Ace uses his Jum Saber to duel Rubangar King, however, he easily slices the Jum Saber. Rubangar King then started swinging his saber towards Jumborg Ace. Jumborg Ace jumped and kicked Rubangar King's silver fin off, causing him to drop his saber. Jumborg Ace then manages to use his Beam Emerald attack again, this time on his back, causing him to fall to the ground, exploding.
- Death Kong King was ment to appear in Rubangar King's place but was cut for unknown reasons.
- Design: Yoshiaki Yoneya
- Powers and Weapons
- Reflective Fins: Rubangar King has fins on his back that can reflect energy-based attacks.
- Saber: Rubangar King has a saber that he can use in fights. When not in use, it is stored on the top of his head.
- Cannons: Rubangar King has cannons hidden in his back which can fire missiles.