In the whimsical world of Nekojima, set against a backdrop reminiscent of feudal Japan, a crafty high-ranking official named Ika Chu harbors treacherous ambitions to expand his opulent palace. However, his plans are hampered by the proximity of the destitute village of Kakamucho, where its weary residents are teetering on the edge of despair. In a bid to eliminate this bothersome hindrance, Ika Chu devises a sinister scheme, enlisting his loyal henchman Ohga and a band of thugs to pillage the struggling village.
As the villagers cry out for salvation, they implore the Shogun to send a new samurai to protect them from the impending doom. In a shocking twist, Ika Chu seizes the moment to insult the villagers further by designating Hank, a hapless dog facing execution, as their improbable savior.
At first, Hank is met with disdain and disbelief, but he soon finds an unexpected ally in Jimbo, a catnip-addled samurai who reluctantly agrees to take him under his wing. As Hank embarks on his quest, he must confront the enormous henchman Sumo, another pawn of Ika Chu, who seeks to hasten the villagers’ departure. With Jimbo’s partisan guidance, Hank overcomes this monumental obstacle, winning the admiration and respect of the townsfolk.
However, as Hank revels in his newfound fame, he grows complacent, neglecting his training and straining the bond with Jimbo. At the same time, Ika Chu orchestrates a lavish gathering to distract Hank while he secretly bribes the villagers to show false adoration for their canine champion.
When the chaos unfolds and Hank returns to find Kakamucho devastated by Ohga's marauders, he engages in a fiery confrontation with Jimbo, ultimately deciding to abandon his responsibilities. Yet, a poignant origami figure of himself serves as a reminders of his samurai vows, compelling him to reconsider his choices.
Undeterred by Hank’s betrayal, Jimbo embarks on a daring mission to infiltrate Ika Chu's opulent palace, intending to rescue Sumo from captivity. With a newfound determination, Hank rallies to join Jimbo, only to discover that Sumo has already escaped.
Now, tasked with the formidable challenge of thwarting Ika Chu's army, Hank must confront his own inadequacies and find the courage to unite his friends against overwhelming odds. The resourceful townspeople of Kakamucho devise a clever ruse, crafting a lifelike replica of their village using flimsy materials that even trick Ika Chu’s thugs into attacking the decoy.
As the false village explodes in chaos orchestrated by Hank, the Shogun arrives, only to be reminded by Jimbo of his notorious past mishaps. In a comedic twist, Ohga inadvertently reveals Ika Chu’s duplicitous schemes, driving the villain into hiding.
With relentless determination, Hank pursues Ika Chu to the extravagant palace, where a surreal confrontation takes place on a gigantic jade toilet, which threatens to flood the town. In a heroic moment, Hank gathers the villagers to create a diversion channel, averting disaster.
With Kakamucho safe once more, the impressed Shogun contemplates bestowing the title of samurai upon Jimbo, but ultimately entrusts it to Hank. Feeling unprepared, Hank chooses to pass the honor to Emiko, an ambitious kitten eager to become a warrior.
As Hank and Jimbo continue their stealthy training sessions, their friendship experiences a heartfelt revival.
In a light-hearted post-credits scene, two guards watch over Ika Chu's prison cell, as he laments his fate, concluding that at least he would be spared the embarrassment of a sequel.
