Tamagotchi: Happiest Story in the Universe!

At Tamagotchi School, the Tamagotchi children wait for the flying library to arrive. While talking about the books, another young student adds a rude comment to Mametchi's dream. Chamametchi recognizes him as Kikitchi, a new student in her class. Mametchi then explains to Kikitchi that the flying library is a flying ship that contains magical books that children are magically transported into and made the main character when they read them. Just then, Kikitchi's sensitive hearing picks up the sound of the ship's horn. Although no one else can hear it, the ship appears after a minute. The Otogitchi Siblings, who take care of the library, bring the ship down, and let down a flight of stairs, which the Tamagotchi children eagerly climb up.

Down in the library, the children eagerly grab various books and open them, which causes various objects to pop out. The Tamagotchi children then jump into different books, causing them to transport into the story. The title theme then plays as the Tamagotchi go on their various adventures inside their stories. Only Kikitchi is alone.

After the children exit their stories and are starting to leave the library, Kikitchi hears a small voice calling out for help. However, due to the fact that he can hear smaller sounds than others, no one else can hear it, and tell him he must be hearing things. Kikitchi responds by slipping a quarrelling Makiko and Memetchi with banana peels

Meanwhile, Mametchi has an idea for an invention, and he rushes home. After several failed attempts, he finally gets his experiment right, but accidentally makes a small creature. He explains that he did not expect his experiment to become and actual living thing, but that the creature can absorb the feelings of others and use it to make other people happy. Mametchi decides to call his new creature "Hapihapitchi".

Hapihapitchi begins to use her power to make people happy. She attempts to use her power on Kikitchi, but Kikitchi runs away, yelling that forcing people to be happy is "nonsense"; depressed by the absence of his parents who're busy opening new buildings. Over time, Mametchi begins to notice many becoming addiction to Hapihapitchi.

At school, the flying library comes again. Kikitchi, who is hiding in a corner, hears the small voice calling out for help again, and begins to search for the source. Hapihapitchi also senses the unhappiness that is connected with the voice, and she begins to search for the source, too. As Kikitchi, Mametchi, Memetchi, Kuchipatchi, Chamametchi, and Hapihapitchi run into each other, a book opens up at their feet, entitled "The World's Happiest Story". They enter the book, where they notice that, unlike the other magical books in the library, they don't become the main character. The story tells of a man named Happy who lived with his dog named Lucky. Because his name is "Happy", he is determined to become the happiest man in the world, so he sets off on a journey, leaving behind his home and his dog. He becomes rich and a hero, but he still isn't the happiest man in the world. As the Tamagotchis follow Happy through the various pages of the story, they notice that the story loops; the end simply brings them back to the beginning. Kikitchi notices that Happy acts similar to how he acted, and he feels regret. However, before the Tamagotchis can help Happy, the school bell rings, and they have to leave the library. Unknown to anyone else, Kikitchi leaves the Library, the book with him.

Back at his house, Kikitchi remembers how he told many children how a tree told him it rain during a festival, and how many rejected him as a liar due to lacking his sharp hearing. Unable to wait, Kikitchi enters the book he has taken home. As he does, however, a tornado of paper engulfs Celebria, and causes the Tamagotchi caught in the tornado to become two-dimensional. Mametchi's family sees the news report on TV, and Chamametchi and Mametchi instantly think of Kikitchi. The family then heads to Mame Laboratories to discuss the problem with other scientists.

At the laboratory, one of the scientists explains that the last page in Happy's story had been torn out, so that he is unable to complete his story. Over time, the book had become unstable, and Kikitchi entering the story caused it to become unstable enough to affect the real world. The only way to save the world was to have Otogitchi, the captain of the flying library, write a new ending with a magic crayon. Papamametchi reluctantly allows Mametchi and his friends to enter the story to save Kikitchi.

Mametchi and his friends enter the book on the flying library ship and find Kikitchi with Happy. They attempt to write several different endings, but they all disappear, meaning that they aren't correct. When he begins to become discouraged, the other Tamagotchi begin to give him ideas of what makes them happy. Kikitchi's idea, which is when someone says "hello" to him during class, has a large impact on Happy, and he begins to get an idea. Unfortunately, the world inside the story begins to fall apart, and the magic crayon is accidentally dropped. Thanks to Hapihapitchi's power, Happy is surrounded with memories, and he finally decides to go back to his home as it was before he left. Otogitchi's sister draws a door, and Happy opens it; suddenly, the book stops disintegrating, and returns to normal. Kikitchi realizes that Lucky was the one calling out to him, and is happy that Happy is now happy.

Suddenly, Hapihapitchi collapses in a field. Mametchi explains that without any happiness, Hapihapitchi would die. Hapihapitchi gets up and weakly sprinkles her last happiness over Kikitchi, who regrets his aggression to her. Happy arrives and uses his happiness to save Hapihapitchi's life.

Back in the real world, the citizens of Tamatown celebrate the return of the heroes. Kikitchi's parents comfort him, by promising to make more time for him from now on. Happily, Kikitchi introduces his parents to his new friends.

The end credits show Tamatown being cleaned up after the paper tornado, and the Tamagotchi children continuing to enjoy the magical story books. A picture inside the wall of Mametchi's home also shows a brief picture of Tanpopo, the main heroine from the first Tamagotchi film.

• Tamagotchi: Happiest Story in the Universe! at IMDb