Medabots—powerful robots granted artificial intelligence through special "medals"—serve at the whims of their owner. They are more commonly used in "Robbatling," a popular combat sport where two medabots face off against one another. In its professional form, Medafighters use their Medabots to qualify for the World Tournament and fight amongst the elite to gain the title of champion.

Elementary schooler Ikki Tenryou has just gained his first Medabot: Metabee, an outdated model with no medal. Fortunately, however, Ikki manages to find a medal in the nearby river; but when Ikki places it into Metabee's head, the latter starts to exhibit strange behaviour. Short-tempered and rebellious, he refuses to obey Ikki's orders. However, to climb the ranks to the World Tournament, Ikki and Metabee must first learn to work together, no matter how difficult the prospect may seem…