Katsuya Jounouchi

Age: 16
Birthday: 25 January
Blood type: B
Height: 178 cm
Weight: 62 kg
Favourite food: Steak and shrimp, curry rice

Jounouchi is Yuugi's best friend. Jonouchi is loyal, heroic, good-natured, brave, funny, friendly, kind-hearted, and loving. At the beginning Jounouchi used to bully Yuugi. When Ushio beats up Jonouchi and Honda, Yugi stands up for them, and it's then that Jonouchi realizes that he was jealous of Yugi's "treasure" all along. Later on that night, he retrieves the last Millennium Puzzle piece and brings it back to Yugi's house, where Yugi completes it and challenges Ushio to the first Shadow Game of the series. Jonouchi is touched by Yugi's behavior towards him and they become loyal friends, forming his own "treasure."
Jonouchi is good at fist fighting and is usually able to take on people bigger than him, such as Bandit Keith (in the second anime, this quality is underplayed). Though not exactly the best gamer in Domino, he develops a better liking to them thanks to Yugi, and he's managed to use his strong points to help Yugi come through in earlier story lines. Later on, he develops an interest in the Duel Monsters game, the latest fad at the time. Though unskilled at first, with Yugi's help, he trains for the Duelist Kingdom and Battle City tournaments for his sister; progressively getting better throughout the series to the point where he could be called a match for Dark Yugi. Jonouchi is shown to have a very kind heart, be selfless and caring, considerate, and eager willingness to help and save those he deeply cares for and loves, but he also demonstrates a near lack of modesty and can be rather rash at times, making him a source of comic relief. He also has an extreme fear of ghosts, mummies, and anything else that could be considered 'creepy'. Jonouchi notes that, before he met Yugi, he was never really motivated for anything. As the story progressed, he learned to channel his anger into games instead of his fists.

(Source: Wikipedia, Yugipedia)