In the year 2122, a young boy named Ikki doesn't have a Medabot and everybody else does, so he's been saving his money for years going back to the same store, looking at the Medabots. One day the owner of the store tries to sell him an old Medabot, then one day a kid from the screws has his Medabot stolen and his leader goes to see the punks who stole his friend's Medabot and they start picking on Ikki's friend, so Ikki runs and finds a medal in the river and he buys the Medabot and saves his friend. his name is Metabee.

When Ikki wins two free tickets to popular Ninja Park, Erika persuades him to take her as his free guest. Ikki's first choice was Karin, but Erika wants to do a story on the park. Ikki reluctantly agrees because Erika took one ticket and wouldn't give it back. The main attractions to the park are the Explosive Ninja Show that features Ninja-Type Medabot Nin-Ninja and Kunoichi (Female Ninja)-Type Medabot Icknite, as well as the Ninja Castle that says closed for renovations. Disappointed, Ikki and Erika proceed to the Ninja Show. As the Ninja Show begins, Ikki and Erika notice that the monsters in the show look very much like the Rubberobo Gang. Seaslug has decided to hold Ikki and Erika captive until renovations are completed on their new base Ninja Castle! The Rubberobo Gang has stolen the Medals of Nin-Ninja and Icknite, and has complete control over them. Intuitively knowing that Ikki and Erika are in trouble, Metabee and Sailor-Multi (nicknamed Brass) come to their rescue.