The small city of Kasukabe announces a sister-city relationship with the Indian town of Mumbai in the state of Hagashimir. To celebrate, the Kasukabe Kids Entertainment Festival is held, with the grand prize being an all-expenses-paid trip to India to perform on a major stage. The five members of the Kasukabe Defense Team—Shinnosuke Nohara, Toru Kazama, Nene Sakurada, Masao Sato, and Bo-chan—decide to enter the dance competition. After rigorous practice, they win and travel to India with their families and the principal of Futaba Kindergarten.

While sightseeing in a bustling Indian market, Shin-chan and Bo-chan wander into a peculiar antique shop. There, they find a strange backpack shaped like a nose, which Shin-chan nicknames Nosengelina Jolie. Inside the bag are two mysterious sheets of paper. Without understanding the danger, Bo-chan, whose defining characteristic is his ever-present runny nose, inserts one of the papers into his nostril. The quiet, gentle, and often overlooked boy immediately undergoes a frightening transformation. He becomes Bou-kun the Tyrant, a powerful and arrogant figure who possesses superhuman abilities and a desire to use the second paper to achieve perfection.

The sudden change shocks Bo-chan’s friends, who try to convince him to return to normal. However, their pleas that he is acting strangely only push him further away, as he feels they never truly understood him in the first place. A pair of eccentric Indian detective brothers, including one named Kabir Kachcha Papad Pakka Papad, explain that the papers have the power to destroy whatever their user desires, turning the bearer into a ruthless ruler. The antagonist Wolf, an Indian IT billionaire, seeks to harness this power for himself, but the transformed Bo-chan proves to be an uncontrollable force.

As the adventure unfolds across real-world Indian locations from the streets of Delhi to the landscapes of Rishikesh, the Kasukabe Defense Team grapples with their friend’s change. They meet Ariana, a popular Indian dancer who hides her own sadness behind a bright smile, who makes them question whether they are trying to change Bo-chan back for his sake or simply because they miss the friend they were comfortable with. The story explores the theme of rejecting the pressure to conform to others’ expectations.

Ultimately, Shin-chan and the others conclude that they want to be with Bo-chan regardless of who he has become, whether he is the quiet rock-collector or the powerful tyrant. Accepting him completely, they work together to remove the mystical paper, restoring his original personality. The adventure concludes with a grand celebration, reaffirming the bonds of friendship that transcend any single identity.