In the fictional Mexican town of Madakueruyobaka, a remarkable new cactus species is discovered, its buds producing a honey that locals soon crave. Futaba Shouji, the company where Hiroshi Nohara works, sees this as a golden opportunity and decides to open a branch office in Madakueruyobaka. The town welcomes the idea, and Hiroshi Nohara becomes the branch president, prompting his family to relocate from Japan. The move means the Nohara family—Misae Nohara, Shinnosuke Nohara, and the rest of the clan—must adapt to a new country, language, and culture as they settle into life in Mexico.
Upon arriving, the family dives into a very different daily rhythm. They sample unfamiliar Mexican foods, try to learn Spanish, and embrace colorful traditional attire as they mingle with locals. The town holds a Cactus Festival in the bustling square, a celebration that quickly becomes a focal point for the community and the newcomers alike. During the festival, one bud blooms into a towering, menacing killer cactus, followed by a cluster of smaller cacti that march through the streets, attacking people, and creating chaos and fear.
As danger spreads, the Nohara family, along with the townspeople, scramble to escape. The crisis peaks when the Mayor accidentally triggers an explosion that collapses the only exit from the city, trapping everyone inside with the advancing threat. In the ensuing scramble, the Mayor and Shinnosuke—Shinnosuke Nohara—find themselves at the center of the chaos. The Mayor feeds Shinnosuke, who suddenly feels the urge to pee. A field nearby becomes the unlikely stage for a pivotal moment: Shinnosuke, in a mix of hesitation and instinct, pees on a small killer cactus, which withers and dies. This surprising, almost comical event reveals a crucial clue: water is the cactus’s weakness.
Armed with this new understanding, the townspeople rally to devise a plan to flood the cacti with water. Hiroshi and Misae coordinate a counterattack that funnels water from the town’s supply into a large balloon named "Sabo-chan," intending to use the balloon as a delivery vessel to douse the Queen Cactus, the main threat. The group—now calling themselves the Madakueruyobaka Defense Group, and joined by Mariacchi, Karorina, and other allies—prepares to execute the plan, with Mariacchi adding his voice to the operation and Karorina lending support as the plan comes together.
The next day, the defense team advances with their water-filled balloon mission. However, the Queen Cactus guards the balloon with its thick tentacles, preventing a clean burst. In a moment of peril, Shinnosuke is tossed into the air by the plant’s assault, and he realizes a hidden advantage: the needle of the KB badge he wears can puncture the balloon. Seizing the chance, he pierces the balloon as he falls back into it, releasing a cascade of water that splashes over the Queen Cactus. The giant plant withers and collapses, and the cacti that had swallowed people whole reveal that those inside were alive all along, now freed from danger. With the threat neutralized, peace gradually returns to Madakueruyobaka, and the Cactus Festival resumes with renewed resolve and joy.
In the aftermath, the mysterious cactus species fades from the landscape, and the Mexican branch of Futaba Shouji is closed. Hiroshi is recalled to headquarters in Japan, ending the chapter of the town’s abrupt crisis. Yet the memories of the festival, the brave defense effort, and the unlikely discovery that water can defeat the cacti linger, shaping the town’s story as a quirky, hopeful adventure that bridged cultures and brought together a diverse cast of characters, including Sumaho and others who stood alongside the Nohara family as they faced an extraordinary threat.
