jonouchi

Jonouchi Katsuya is a 16 years old fictional character of the manga and anime series Yu-Gi-Oh! And known as Joey Wheeler in the American version. He was a member of Hirutani's gang when he was in middle school, and a problematic street kid. But after being saved from Ushio, a bully, by little Moto Yugi, he learns to be a better person and leaves the gang. His other two friends are Hiroto Honda (Tristan Taylor) and Mazaki Anzu (Tea Gardner). In the manga, Jonouchi must work in multiple jobs to repay his father's debs, since he's a gambler and alcoholic, and they monetary situation was not the best. Jonouchi's parents divorced when he was 10, and his sister Kawai Shizuka was brought away along with his mother. In the manga and Duel Monster's anime, Katsuya enters the Duelist Kingdom Tournament in order to win the money prize and pay for his younger sister's eye-sight surgery. It's very common to pair him up with Kujaku Mai (Mai Valentine), since in the manga and anime series they seem to have romantic feelings for each other. This was denied by Takahashi Kazuki (creator), who claimed it was purely friendship. Another character commonly paired up with him is Kaiba Seto. Many fans state that although Moto Yugi is Kaiba’s former rival, said boy never loses a chance to insult Jonouchi, which leads to think that he somehow acknowledges his existence a little bit too much. Other fans declare that Kaiba is secretly attracted to him, and plays the role of ‘the boy that likes the little girl and teases her to call her attention’. And seeing as Jonouchi didn’t kill him yet, he may return that feelings as well.
Nothing of the above has been confirmed by Takahashi Kazuki, but even a blind man can see the sexual tension between those two. 

Read the manga and see how Kaiba and Jonouchi act around each other, or simply pay more attention to the series.