Lamune, a typical 4th-grade boy engrossed in video games, stumbles upon a mysterious game sold by a wandering girl. After mastering the game, he is summoned by Princess Milk from the game world as the long-lost relative of the legendary hero Lamuness. Tasked with awakening the Guardian Knights, Lamune unlocks Tama-Q, his mechanical advisor, and sets out to free these sentient mechas. However, his quest is challenged by the sinister Don Harumage and his henchmen Da Cider and Lesuka.