The Hinatas and frogs go on a day trip to a hot spring for Labor Day, but Aki freaks out when she sees a wild monkey in the bath. Her panic leads to an army of more monkeys descending on the hot spring. Later, Keroro and the other members of his platoon are inspired to bake Keronian bread, but little do Fuyuki and Natsumi know that this alien version of bread is more like a battle between edible gargantuan mechs that look like their respective bakers.