Age: 16

Birthday: 28 February

Blood type: B

Height: 179 cm

Weight: 64 kg

Favourite food: Chinese cuisine

Least favourite food: Vinegared food

A talented game inventor and is also the creator of Dungeon Dice Monsters (anime and English manga) or Dragons, Dice, & Dungeons (Japanese manga). According to his father, Mr. Otogi (or better known as "Mr. Clown"), Ryuji was born and raised as a brilliant games player in order to fulfill his father's revenge on Sugoroku Mutou. Sugoroku had defeated Mr. Otogi in a Shadow Game called the Devil's Board Game, causing him to age 50 years in one night as a Penalty Game. Ryuji was transferred to Domino High School, where Yugi Mutou (Sugoroku's grandson) goes to school. His father used this as an opportunity for Ryuji to defeat Yugi in a series of games and fulfill the family's revenge, taking the Millennium Puzzle for himself.[5] Unfortunately for Mr. Clown, Ryuji ends up being moved by the games he had with Yugi and cannot bring himself to hate him, ultimately rejecting his father's revenge and eventually joining Yugi's circle of friends. He is somewhat serious and quiet, but also level headed and very intelligent.

In the second anime, the influence of Ryuji's father is omitted entirely and Ryuji's personality is rewritten. Instead, it is explained that Ryuji befriended Pegasus, who became fond of Dungeon Dice Monsters, and wanted to help him market the game. Following his defeat by Yugi, Ryuji's idol is no longer interested in their earlier deal. Angry and bitter, he blames Yugi and believes he cheated in his match against Pegasus. After learning the truth, he befriends Yugi and the others and will often join them on their adventures. Despite his arrogance and being one of the more negative, sarcastic members of the group, he is still fairly smart and level headed. His personality often causes conflict with Honda, especially over Shizuka, who they both have a crush on in the anime.