Yugi and Imori's Dragon Cards game

Yugi and Imori's Dragon Cards game was a Shadow Game of Dragon Cards in the Yu-Gi-Oh! manga between Yugi Mutou and Imori. In the first series anime, Yugi and Imori played Dragon Block instead, although the rules and moves were largely the same.

Prior events
By reading books his grandfather left him on games and Ancient Egypt, Imori learned "The one who solves the Millennium Puzzle, shall gain the thousand ways of the Shadow Games and become the guardian of darkness.". He knew that Yugi had solved the Millennium Puzzle and judging by how people had stopped bullying him since he got it, assumed Yugi had gained these powers.

Imori also found the sealed Dragon Cards his grandfather had left lying in their shed. He brought it to Kame Game to ask the Mutous if they knew anything about them. Sugoroku recognized them and warned Imori not to break the seal as it would created a warped power.

Imori spend the next few days studying the cards and their game. He then stole the Millennium Puzzle while Yugi was swimming and left a note telling him to come to room C alone if he wanted it back.

When Yugi arrived in room C, Imori told him what he had learned about the Millennium Puzzle and in order to claim its power for himself, he needed to beat Yugi in a Shadow Game. Imori then took out the Dragon Cards and removed their seal and warned Yugi that texts about Ancient China say that if a Shadow Game doesn't take place when the seal is broken the people of the land would suffer eternal disaster.

Imori told Yugi the rules of the game and that the loser would have their soul sucked into the soul-eating jar. Without the Millennium Puzzle, Yugi had to fight the game by himself.

The game
Imori went first and drew a Level 4 water dragon. Since he had another Level 4 water dragon in his hand, he planned on waiting to get the third copy and discarded a Level 1 metal dragon. Yugi drew a level 5 fire dragon and discards a Level 1 fire dragon.

As the game progressed, Imori figured out which elements Yugi was collecting.

Finally Yugi gathered and Summoned a Level 5 fire dragon, "Huo Long" and a metal dragon, "Jin Long". Imori then Summoned his dragons, levels 3 and 4 water dragons, "Shui Long". Water was strong against fire and metal powered-up water, so Yugi had little chance of winning. The two water dragons used their flood attacks and defeated Yugi's dragons.

Aftermath
The level 4 "Shui Long" reached inside Yugi and pulled out his soul. The dragons then returned to the soul-eating jar, taking Yugi's soul with them. Yugi collapsed onto the table. By doing so, he touched off the Millennium Puzzle allowing Dark Yugi to take control. Dark Yugi challenged Imori to a rematch. Imori accepted, needing to beat both Yugis to gain the powers of the Millennium Puzzle.