Sho Marufuji (Syrus Truesdale in the 4Kids dub) is the Jaden Yuki's best friend, he follow him in every adventures. He is a former student of Osiris Red, then Ra Yellow, and now Obelisk Blue (In the season 3 and 4). A decent duelist who doubts himself because his older brother Ryo Marufuji, but the good influence of Jaden and his others friends make him more confident.
He was voiced by Masami Suzuki, who voiced Ghost Kotsuzuka from the previous series, in the Japanese version and Wayne Grayson in the English version.
Sho is a insecure and unconfident duelist. However, he not only grows into becoming a better duelist, but a more brave and confident person.
He is a very loyal friend, often thinking of Judai as a second big brother figure.
Sho is considered to be the "weaker" younger brother of Ryo Marufuji who attends Duel Academia, originally residing in the Osiris Red dormitory along with Hayato Maeda and Judai Yuki. Sho has made progress as a duelist throughout the series. From the onset, he faced Judai in preparation for a tag team duel, but, priding himself on finding a way to outdo his roommate, overlooked the abilities of his own cards. It was for this same reason that Ryo forbade him from using the "Power Bond" card, for Sho was unable to cope with its potential drawback.
During the second season, Sho is given an opportunity to advance to Ra Yellow, should he be able to defeat Ran Kouchou. Feeling that he should not shoulder his brother's legacy, Sho gives his "Power Bond" card to Jun Manjoume to pass to Judai before the start of the Duel, though Judai convinces him to put it back in his deck after the duel.
Sho develops a rivalry with Tyranno Kenzan over which of the two is better suited to being Judai's best friend (in the Japanese version, it is over who has the right to call him "big brother"). They constantly argue and fight, prompting their repetitive separation by Asuka Tenjouin. By episode 64, their rivalry comes to a temporary halt, when the two duel to settle matters once and for all. Before the last blow is dealt, Kenzan discovers that Sho went without food or sleep to search for Judai, who had gone missing since his defeat at the hands of Edo Phoenix. Seeing Sho's devotion to their friend, he chose not to activate his "Jurassic Impact" card, which would have wiped both players out simultaneously.
During the field trip to Domino City, Sho teams up with Kenzan in a duel against the first duo of the Four Monarchs, Koorimaru and Ikazuchimaru. Although the two are pinned down by their opponents, who tuned their decks specifically to combat their cards, they end up pooling their efforts to combine their monsters into "Super Vehicroid Rex Union". Despite their teamwork, however, Koorimaru ends the duel by wiping out all players but himself, and promptly drags them to his master's lair, from where they are transported to Kaiba Land as bait for Judai and Edo by order of Mizuchi Saiou.
As he observes his brother's actions following his "rebirth," Sho notes Ryo's newfound disrespect for his own cards and opponents. He dismisses the barbaric persona, refusing to believe that his brother has sunk so low. Determined to bring his brother back to his senses, Sho acknowledges the inevitability that the two of them will face one another. During the Genex Tournament, Sho and Ryo duel, they are hooked up to electrodes, just as Ryo and Mad Dog Inukai were in the Underground Duel. Despite his best efforts and Judai's secret move to place "Power Bond" back into his Deck, Sho loses, but he does not give up in hoping that his brother can be returned to his former self.
Shortly after the beginning of the third year at Duel Academia, Sho advances to Obelisk Blue. As a result of survival duels being called for by Professor Cobra, Sho becomes self-conscious of his worthiness to wear the outfit of the elites, and sets out to prove himself. In the Japanese version, he also wishes to adopt his brother's discarded title, and thus merit the name of "Kaiser Sho" (カイザー翔, Kaizā Shō). Inspired by Judai's match with Austin O'Brien, however, he decides to remain in Ra Yellow, and sets aside his goal for the future. (In the English version he quits the Obelisk Blue dorm stating that blue was not his color and he left Obelisk to protect Judai). After Duel Academia is transported to the first alternate dimension, Sho falls to the Duel Zombies and becomes one himself.
Later, when Judai and company venture into another alternate dimension to rescue Johan Andersen, Sho is the only one of Judai's closest friends who isn't sacrificed by Brron. After Judai wins, Sho verbally scorns him saying he wants nothing to do with him and up leaving him. While separated from the others, Sho decides to act as an observer, but later reunites with Edo and Ryo when Judai is released from his possession. After Ryo loses to a Yubel-possessed Johan, Sho watches Ryo die and fade into particles of light before breaking down in tears.
In season 4, Sho advanced to Obelisk Blue again. Sho later attempts to finish Ryo's duel with Makoto Inotsume after Ryo becomes too weak to duel, but immediately regrets his decision later as he begins to develop the same heart problems as Ryo because of his use of the "Cyberdark" Deck. However, Sho manages to overcome his problems and defeat Inotsume, thus inheriting Ryo's Cyber Dragon Deck later on and promises to improve it. However, he still later falls to him, and is absorbed into the World of Darkness. It is shown within the World of Darkness that Sho fears that he will be unsuccessful at creating a Cyber Legacy Pro League with Ryo (as it is his brother's dream) and that he will have to be the successor of the Cyber Legacy when Ryo becomes greatly ill (as he has his limits). He also fears that he will be unable to make this dream come true due to few to no people and sponsors being interested in it. It is also shown that if Ryo dies when Sho is still unsuccessful at creating a great Pro League, then he will feel relieved that he is finally released from trying to create something he could not succeed at creating. He is revived after Judai defeats Darkness.