Little Battlers Experience

Little Battlers Experience, also known as Danball Senki (Japanese: ダンボール戦機, Hepburn: Danbōru Senki; lit. "Cardboard War-Machines"), or simply LBX, is a series of action role-playing video games created by Level-5, involving small plastic model robots known as LBXs (standing for "Little Battler eXperience") that fight on dioramas made out of cardboard, with the main character setting out to battle against LBXs created by other characters.

Source: Wikipedia — Little Battlers Experience (CC BY-SA 4.0)