Doraemon: Nobita’s Diary on the Creation of the World

Nobita reads a picture book about Adam and Eve and ponders that their descendants will face many difficulties because of their mistake. Doraemon reminds him that his summer vacation homework must be done. This opening frames the science-fiction journey to come.

He goes to check his friends' research but finds everyone already busy with their own tasks. The effort leaves him discouraged, yet determined to complete his own project. The pressure pushes him toward the World Creation Set.

Doraemon brings the World Creation Set to help with Nobita's project. Nobita starts crafting a new Solar System using 'elements of the universe' dust and records the process in a diary. He describes the steps as if building a living model of the cosmos.

Nobita gets bored and is chased by Gian for doing homework, while Suneo kicks him out. In his distraction, the artificial sun devours the other planets. Doraemon reverses time in the set, and they glimpse how life on Earth might form, from cells to early fish-like organisms.

Doraemon uses the Evolution-Devolution Beam on the ancestral land vertebrate Eusthenopteron to accelerate its evolution. A bug accidentally hits the rays, causing unforeseen consequences in the evolving life. The team witnesses rapid changes and growing challenges in their Earth-forming experiment.

That night Gian attempts to meet Nobita to apologize and join the project but witnesses a strange falling star. He follows it and spots two humanoid mantis-like creatures; Time Patrol intervenes, making Gian think it was a dream. The incident hints at a larger cosmos watching their project.

The next day, the first fish are seen walking on land, followed soon by the dinosaurs, bringing joy to Doraemon and Nobita. An asteroid strikes, wiping out the non-avian dinosaurs and leaving the survivors to adapt. Nobita is devastated, but Doraemon offers comfort and motivation to continue.

Gian and Suneo join the venture after Nobita invites Shizuka to complete the group; together they enter Nobita's universe and witness Earth during the Ice Age. They help a group of primitive kids who resemble Nobita, Suneo, and Gian, and Nobita is hailed as Kami by them. Gian publicly reveals the project, drawing the mantis-like creatures' attention.

The trio observes rudimentary agriculture, witch doctors, and human sacrifices signaling the dawn of civilization. They meet descendants of the primitive kids and confront a giant two-head centipede-like monster on a mountain, which they manage to defeat. Sunemaru's daughter vanishes during these events, spurring a frantic search.

Suneo and Gian decide to cancel their part of the project to go on vacation, which angers the others. The duo is kidnapped by the mantis creatures that had been glimpsed earlier, threatening the group's progress. Doraemon and Shizuka's absence leaves Nobita to face the situation with the rest of the team.

Nobita heads to Japan and meets an elderly herbal merchant named Nobina who is treated poorly by Sunemaru, a royal doctor. Nobina rescues an injured beetle-like creature Nobita calls Chunko, and a journey through a cave leads to an exotic kingdom where he earns treasure and relief from poverty. The events connect his journey to the larger project across cultures.

Nobina and friends encounter insect-like citizens who create an illusionary demonic entity to frighten others. The illusion is revealed as the gathering of thousands of insect people and sets up the ongoing conflict involving the surface world. The daughter of Sunemaru is involved in these events and becomes a focus of the search.

The group travels to Taishō-era Japan and follows an air balloon to a giant hole in the South Pole. They are confronted by a god-like man who Doraemon reveals to be another insect congregation; Doraemon disintegrates him, allowing them to proceed. They reach an underground world inhabited by mantis-like humanoids.

The mantis-like humanoids threaten the surface world, and Nobita reveals his role in starting the world. Doraemon gives them a World Creation Set of their own, enabling the mantis to establish their ideal world and potentially save both sides. The surface is saved as a result of this uneasy compromise.

Nobita decides that neither humans nor mantis-like beings need his help anymore and leaves forever. The end credits reveal that all four of the main human characters have jointly completed the project, signaling a closing of the loop on Nobita's universe experiment.