Takamine Kiyomaro, a depressed don't-care-about-the-world guy, was suddenly given a little demon named Gash Bell to take care of. Little does he know that Gash is embroiled into an intense fight to see who is the ruler of the demon world. All of the demons have to pick a master on Earth and duke it out with other demons until one survives. Needless to say, Kiyomaro becomes Gash's master, and through their many battles, Kiyomaro learns the importance of friendship and courage.

The English release of the series under the name Zatch Bell! was edited, removing things like blood and nudity with Gash (Zatch in the English version) wearing boxers instead of being fully naked. The uncut Japanese version of the series has never seen an official English release.

VIZ Media licensed and dubbed the first 104 episodes of Konjiki no Gash Bell!! under the name Zatch Bell!, but only released the first 52 episodes on DVD. In December 2013, Flatiron Film Company later released the first 104 episodes on DVD.