Yuji Matoni Nakajima is the 7th Protagonist in the Yu-Gi-Oh! series, he is a 16 Aged teenager, that has no origins.
He lived in all protagonist's timelines from Jaden's till Yuya's Timeline, Except yugi's one. His age didn't change from each timeline, It means he is probably not a human, people say that he is a robot from the ghost prototype, or a dueling spirit (Like Astral). No one knows his origins, even he doesn't, he saw the satellite and new domino city and lived there, and saw the split of the united world, without being divided. He were in the Slifer Red dorm in the dueling academy, along with Yuki Judai.
He rented an apartment to live in, He didn't have money, so He Have been kicked out of it. He went in the streets, without a house, a duelist named Giron Inoue challenged Yuji for a duel, Because of his past knowledge that Yuji is not a normal duelist, Yuji have won using his Mysterious Dragon, and got the people to like his duel, he then after everyone have gone, he stayed in the dueling stadium, a girl started following him in the streets to see what will he do, his older cards got stolen once and wanted to bring them back, after becoming a professional duelist, he always dueled to challenge people, and save others. In one day he heard about turbo dueling championship and wanted to try it with Yumi(the girl who brought him to her house), she and her dad worked on a duel runner, Yuji had a duel runner in the past, that were so fast and loud, it made a little girl cry when he just passed by her, so he went to his old abandoned garage, anf found it there, and fixed it, to make it one of the best duel runners ever, as he entered the contest, he started winning many duels, until he dueled with Kevy Yamamaoto, one of the best duelists and a great synchro user, Kevy dueled with Yuji, but Yuji weren't a match for his Whirlwind Dragon, So Yuji treated Kevy as his rival, and requested a rematch, the rematch ended by a draw, so Kevy saw that Yuji isn't a regular duelist, Yuji requested from Kevy to enter with him in the new "Team Mysterious". New names and decks will be revealed soon.
He uses a Mysterious Cosmic Star Deck, he is a synchro user at the first but then he tries all the other summoning methods to turn a master duelist, he used many decks before having his Mysterious deck, like a WATER deck and an earth one, but now he is in one of his strongest decks.