The card game Duel Monsters has become all the rage in Domino City. The rules are simple: two players, known as Duelists, fight each other with the monster cards they have collected in their decks and deduct Life Points. Each Duelist starts with a total of two thousand Life Points, and whoever loses all of them first is defeated in the battle. One day, a timid boy named Shougo Aoyama buys a deck that contains the Red Eyes Black Dragon, a legendary card said to bring victory to those courageous enough to fight. Soon, word of the card in Shougo's hands begins to spread, eventually reaching the competitive Duelist Seto Kaiba. Desiring to collect the strongest cards in any way possible, Kaiba invites Shougo and his rival Yuugi Mutou to a Duel Monsters tournament—but will Shougo be able to overcome his fear of losing?

Obsessed with revenge against the King of Games, Seto Kaiba commences an excavation in Egypt to find the fragments of the Millennium Puzzle, which once retained the spirit of the counterpart Yuugi. However, a cloaked man steals two pieces of the Puzzle and disappears before it could be reconstructed. Meanwhile, now in their final year of high school, Yuugi Mutou and his friends plan for their futures, unaware of the danger lurking close by. Yu☆Gi☆Oh! The Dark Side of Dimensions tells the tale of vindictive forces distorting reality in whatever way they please. Will Seto and Yuugi move past their differences and save the world, or will Seto's own greed get the better of him?

As time marches forward, Rin Shima, Nadeshiko Kagamihara, and their friends have grown into full-fledged adults. Now with careers and responsibilities, they can no longer freely spend their days camping and adventuring. However, Chiaki Oogaki, who currently works for the Yamanashi Tourism Organization, reunites the group as she comes up with an exciting proposal—to build a campground together to revitalize an abandoned patch of land from their homeplace, the Yamanashi Prefecture. Motivated by this ambitious project, the girls combine their efforts to create an environment where future generations can enjoy unique moments as they once did, all while reminiscing the charms of camping from their high school days.

The second movie in the Washio Sumi no Shou trilogy.