Metabee and Ikki wait for Erika and Brass who arrive late. They all run to the ninja show but they arrive when the show has just ended. Erika yells at Ikki for being slow and he yells back at her, saying she was the one that was late, starting a fight. Brass asks what are they going to do and Erika says they can check the rest of the park until another show starts, while Ikki complains that she could simply have said that instead of yelling at him for no reason.
They all have some fun eating candy cotton, playing on the tirolean, and Ikki even scores a prize at one game, but then they get to the fun house and see it's closed. Erika yells at Ikki blaming him for that because he had invited her, he rubs on her face that she invited herself and both start arguing, while their Medabots just sigh.
Brass has the idea to take them to a nice place close to a waterfall so they could chill out, but Ikki and Erika sit on the same rock and fight over who sat there first. Some minutes later they decide to apologize to each other, but also start an argument over who has apologized first and give up on the idea of peace. It's then that Metabee spots Rokusho and Erika is able to take a few pictures of him right before he leaves saying: "You won't get away with it." They don't understand why Rokusho said that and decide to go to the ninja show.
In the ninja show, Ikki jumps excited trying to draw attention to himself, so he could be chosen to go to the stage, but Erika yells at him, saying she can't take pictures with him jumping like that by her side. The two argue a lot and the guys dressed as monsters choose both to go to the stage. They pretend they're in danger and call out for the ninjas. The Medabots come and truly attack the "monsters", scaring everyone, making the spectators run away, dragging Metabee and Brass with them. After they are all gone, the Rubberobos reveal themselves and kidnap Ikki and Erika.
The two kids are brought to the Rubberobos' hiding place: the fun house. The gang reveal their plan of getting Medals from the Medabots in the Ninja World and tell them they removed the Ninja Medals and replaced them with their Medabots' Medals. Meanwhile, Metabee and Brass run inside the fun house, looking for their Medafighters. They climb up some stairs and find a door, which Metabee opens, revealing another door. They see a button saying "Don't Push", but Metabee presses the button anyways, triggerring a trap that opens the floor below them and sends them falling to the darkness.
Ikki notices the rope tied to Erika and him can be easily removed and starts working on a plan to get them out of there. Metabee and Brass appear climbing stairs again and find another door very similar to the one that found a while ago, but this time, the button says "Push". Metabee presses it and another trap is triggered, making a mole under the floor push them upwards. Ikki and Erika are about to sneak past the Rubberobos when the ground breaks into pieces because of an elevator that was going upwards in high speed. After the smoke disappears, they see Metabee and Brass, then grab them and run.
The Rubberobos send an alert to all of the gang, so they look for the four fugitives. Squidguts climbs the stairs after the four, but Ikki steps on traps that make boxing gloves come out of the walls and hit him, then the boy steps on a final trap that makes the stairs become a ramp, causing him to slide all the way to the other floor. The kids and the Medabots see other members of the gang coming out of the walls and run. After they notice there are too many, they decide to separate: Ikki and Erika going to one side and Metabee and Brass to the other.
Ikki and Erika end up on the attic and find out there are many Rubberobos there. Erika uses her camera's flash to blind them all and the two run. Meanwhile, Metabee and Brass are running in a large room with the ninja Medabots throwing bombs at them. The bombs make a hole on the wall and send the two Medabots flying towards the roof. On the way, they find Ikki and Erika climbing the stairs and Metabee tells them to meet them on there.
They reach the roof and take a moment to breath, but the Rubberobos find them. Surrounded and with nowhere to go, they decide to Robattle against the ninjas. Mr. Referee appears in a golden fish costume, but he slips and falls from the roof, warning that it wouldn't be an official Robattle without him. The Rubberobos take the chance and play without the rules.
Icknite disappears and throws a smoke bomb behind Metabee and Brass. Nin-Ninja runs around the two very fast, creating illusions of himself. Metabee shoots at the illusions, but doesn't hit the actual Medabot. A knife comes from the middle of the illusions and hits Brass. Then they throw shurikens and bombs at her, dealing a lot of damage and sending her flying off the roof. She falls and hits another roof.
Erika is scared and says she'll throw in the towel, otherwise Brass would be destroyed. Ikki tries to convince her to fight, without success. The Rubberobos throw chains at Metabee and try to capture him, but he shoots them and gets free. His medasense tingling warns him about Rokusho's presence. Rokusho tells him they all must rely on teamwork to win the battle. Ikki then manages to get Erika to work with him.
Mr. Referee appears again, now dressed as a samurai, and starts the battle. Icknite uses the same Leaves Camouflage tecnique, but this time Brass uses her scanning system to warn Metabee of her presence, preventing her smoke bomb attack. After Icknite was countered, Nin-ninja used his multiplicity tecnique. Ikki countered it telling Metabee and Brass to stand back-to-back and shoot everywhere, move that made them finally hit Nin-ninja. Metabee uses his right arm to give powerful shots against the ninjas and causes and explosion. But then two knifes with bombs attached to them are thrown against him and he uses his left arm to protect his face.
After a huge explosion, they see his left arm's function ceased and his vision sensor was at 20%, which made him nearly blind. Ikki becomes nervous, that battle was harder than they thought. The ninjas jump in the air and prepare for their final attack: the special ninja sword. Erika and Ikki are desperate, thinking that was the end, but Metabee and Brass come up with a plan by themselves: Metabee points his right arm upwards and allows Brass to aim for him.
The ninjas throw bombs against them, but all missed. Metabee shoots and hits Icknite, ceasing her function, but Nin-ninja is still proceeding with the attack. When the ninja Medabot strikes and an explosion is heard. When the smoke disappears, they all see their Medabots frozen with Nin-ninja's sword touching the ground and passing through Metabee and Brass right in the middle of them. After a few seconds Nin-ninja colapses, his funtion had ceased and Metabee and Brass were victorious.
The Rubberobos run away with a firework and Rokusho throws the actual Ninja Medals to Metabee. After Ikki, Erika Metabee and Brass give the Medals to their owners, they mention something about acting in the ninja show again, with Metabee asking what part he would play and Brass replying he'd play a monster. Erika notices she didn't take any pictures of the ninjas in battle and starts a fight with Ikki, blaming him for that. Their Medabots just sigh, wondering when will those two finally stop fighting.