Zane Truesdale, known as Ryo Marufuji (丸藤 亮, Marufuji Ryō) in the Japanese version, is a character in the Yu-Gi-Oh! GX manga.
He is at the top of the class, and is described as "Number one ranked in practical skills". His "Kaiser" nickname is retained even in the English edition of the manga. When they were children, Zane gifted Syrus with "Transformation". He believed that Syrus was too nice to be a Duelist as he cared for his opponents too much. He came to this determination after witnessing Syrus throw a Duel against a friend of his named Masao. Zane competed in the junior leagues when he was a child, alongside Atticus. The two "dominated" the title of Junior Champion. During this time, Zane and Atticus met American Duelist Aster Phoenix. When they departed for Duel Academy, the title would be won by Chazz Princeton.
Zane studied abroad in America with Atticus, where he represented Duel Academy well. He returned to Duel Academy months later alongside two American students - David Rabb and Reggie MacKenzie. A tournament was organized, with the winner being permitted to Duel Zane. He witnessed Syrus defeated in a Duel by David, with David coming to the conclusion that if the brother of the Kaiser is that weak, perhaps the Kaiser himself isn't as strong as his reputation implied. Syrus defended Zane, telling David not to insult his brother. Zane came to the conclusion that Syrus had done a lot of of growing up when he'd been away. Syrus made it to the top eight of the tournament, and though he is defeated by Chazz, Zane came to believe that Syrus had matured into a true Duelist. Zane is confronted by Bastion Misawa, as the latter is jealous of Zane's closeness to Alexis Rhodes, whom Bastion has a crush on. He would declare his intent to face Zane as "both a Duelist" and "as a man". Zane told him to win the tournament, as that would be the quickest path to Dueling him. As Zane witnesses Syrus, Chazz, Alexis, Bastion and Jaden Duel in the tournament, he is greatly impressed by how skilled the first-year students are. The eventual winner of the tournament was Chazz, and it was announced that he'll face Zane at an arena built into Duel Academy's volcano.
Chazz appeared to have an early advantage, with Zane calmly countering him. Zane Summons "Cyber Eltanin" with a combination of "Emergency Cyber" and "Born from Draconis". He defeated Chazz with this creature, with Chazz not even dealing him a single point of damage in return. He did compliment Chazz on the latter's skills, however, addressing him as "Junior Champion". Zane would watch the Tag-Team Duels between the American and Japanese students with Atticus. Zane witnessed Syrus and Alexis rushing towards the warehouse at the docks, and opted to follow them. He met Midori Hibiki there, who had followed the spirit of "Light and Darkness Dragon" to the same location. He would witness Tragoedia fall to Jaden and Chazz. Years later, he watched Jaden's world title match against Koyo Hibiki, while wearing his "Hell Kaiser" outfit from the anime.
Zane plays a Cyber Style Deck. Many of his cards are based on stars, particularly those in the constellation Draco. In this continuity, Zane utilizes a far more defensive strategy than his anime counterpart. He bides his time with cards such as "Cyber Larva" while gathering the components for a winning move.