The movie begins with Fuyuki Hinata and the Keroro Platoon exploring an abandoned temple in the mountaintop city of Machu Picchu in Peru. While on the exploration, Keroro accidentally sets off a trap, and by chance they find a hidden chamber with a large blue crystal in the center, on a stand that has a key in it. Keroro leans on the key, causing the room to activate a mysterious machine, this caused the entire temple to shake. As soon as the group realized what was happening, they run out of the room. While running, Keroro accidentally loses his Kero Ball while Fuyuki catches a fleeting glimpse of a glowing young woman as he is running out, and tells Keroro that there was a girl in the room, but he is forced to leave the room before he can say anything else. The group successfully escapes, while the girl (now sprouting a pair of glowing wings) watches them leave - while back in the chamber, something is growing within the crystal...

Another Kiruru appears in the South Pacific, but it was defeated by two unknown entities that look like Keronians, with subtle differences. Meanwhile, Keroro and the gang goes for a trip sponsored by Momoka to a private island. There, an alien named Meru, who claims himself as the prince of the deep sea, captures them, and aims to make Natsumi his princess, and that they had captured Keroro, who pleads to them to assist the Keroro Platoon, only to be kicked out.

Seeking to unlock the mystery of a strange stone statue that looks exactly like their Sergeant, the members of the Keroro Platoon find themselves engaged in a great adventure.

Mysterious giant beings called "Ryū no Shippo" (Dragon Tails) appeared across the world. Due to the danger it could bring, the Keroro Platoon did a worldwide research on the Dragon Tails, but Tamama suddenly disappeared during the research. Because of this, the whole platoon started their search for Tamama and ended up in Mont-Saint-Michel, France where they met mysterious girl named Sion, who holds the mysterious Ryū no Hon (Dragon Book). But little they know about the secrets about her and the worldwide calamity that would destroy the entire world, as they know it...

This is episode 0, the prequel to the main Keroro Gunsou anime series. KeroZero was shown in theaters with Keroro Gunsou Movie 4.

keroro! A brand-new campaign to invade Pekopon begins!

《Keroro军曹》是日本的一部喜剧动漫作品，原作漫画版作者为吉崎观音，原是针对成人读者的漫画，其後由日升动画公司改编的动画却吸引大量儿童读者。动画版于2004年4月3日至2011年4月3日在日本播出，一共七季358集，目前已经全部播映完毕。而军曹亦评为无线版《福星小子》。香港无线电视于 2006年7月3日首播，目前已播到第七季

《Keroro军曹》是日本的一部喜剧动漫作品，原作漫画版作者为吉崎观音，原是针对成人读者的漫画，其後由日升动画公司改编的动画却吸引大量儿童读者。动画版于2004年4月3日至2011年4月3日在日本播出，一共七季358集，目前已经全部播映完毕。而军曹亦评为无线版《福星小子》。香港无线电视于 2006年7月3日首播，目前已播到第七季

某个优闲的日子里，冬树与KERORO小队一起去参观印加帝国遗迹—马丘比丘。他们在那里进入了一个迷宫，但Keroro粗心大意地误触了连环陷阱，大家只能赶快往前奔跑逃命。而冬树在逃跑的同时，瞥见了一个伫立在迷宫之中，一动也不动的神秘少女。冬树就这样带着对少女的疑问回到了东京，并渐渐遗忘了这个事情。 然而，最强的敌人就在此时无预警的现身。这个敌人的相貌竟然跟Keroro无太大分别，并且准备好带着优秀的部下，开始展开侵略世界各地。Keroro小队这次，将为了蓝星的命运而战。

该作讲述了来自Gamma星云第58号行星的宇宙侵略军特殊先遣工作部Keroro，为了给征服地球做准备而潜入了日向家，结果因行迹败露被日向冬树和日向夏美发现并生擒。