Sergeant Keroro and his four subordinates came from the planet Keron to the Earth to conquer. However, without notice, they began to enjoy the life on the Earth. Keroro was supposed to stay with Hitana to get the chance to conquer the Earth, but he became friend with Hinata's son, Fuyuki. 
Today, as usual, Keroro goes to buy his favorite Gundam plastic model with Fuyuki. On their way home, they find a small shrine, and enter. There, they find a vase, and happens to break it. Since the next day, strange things happen all over the town and people are in panic. Inside the vase, Kiruru, Keron's ancient ultimate weapon was sealed. At the moment, Mirara who holds the secret of the Kiruru appears and informs them of the only method to save the Earth. However... 
(Source: AnimeNfo)

Keroro is a frog-like alien sent from his home planet on a mission to conquer Earth. But when his cover is blown, his battalion abandons him and he ends up in the home of the Hinata family. There, he's forced to do household chores and sleep in a dark basement that was once supposedly a prison cell haunted by the ghost of an innocent girl. He even spends his free time assembling Gundam model kits. During his stay, Keroro meets up with subordinates who were also stranded during their failed invasion. 
 
(Source: Anime News Network)

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