Sergeant Keroro (aka Sgt Frog), is captain of the Special Advance Team for Space Invasion, for planet 58 in the Gamma Storm Cloud System.
He is sent on a mission to Pokopen (aka Earth) to collect information for his planet's Invasion Force!
But all does not go to plan when he crash-lands his spacecraft and is forced to take shelter in a nearby house. The children of said house, Fuyuki and Natsume, take him in as a friend but when the frogs of planet 58 find that Keroro has blown his cover, he is left to fend for himself on this hostile planet....
But it he the only Invasion Agent to have failed his quest on Pokopen...?