The objective of the game is to save DeMille's girlfriend, Patharan, and the Ketchup Kingdom from King Abira by going through every village to obtain the missing parts of a robot that can give anyone access into the Gimmick Palace, a tower-like structure with a tomato on it.

In lieu of random encounters, Tomato Adventure displays enemies moving around on the overworld, with battles being initiated when DeMille makes contact with them.

Then, a mole named Rereku tells him that in order to pass through the wall, DeMille has to defeat the six Super Kids and obtain the six key items called Toy Parts.

While DeMille goes on his adventure, he befriends some people for them to join forces with him to defeat King Abira and save Patharan and the entire Ketchup Kingdom.

[1] They got the name from an idea of a game structure that utilizes gimmicky, toy-like controls that make it an RPG with action elements.

After noticing that, Nintendo requested AlphaDream to redevelop and rename Gimmick Land as "Tomato Adventure" for the Game Boy Advance.

Nintendo also requested AlphaDream to add some easily recognizable characters in which reflects the new title, so that the game would have a more marketable image.