|“||You finally remembered, didn't you? I've been keeping it for you. Because it's a valuable memory of yours||”|
— Shin Nitta, Episode 25
Shinemon Nitta, more popularly known as Shin Nitta, is the uncle of Misaki Tokura, and in the Cardfight!! Vanguard anime and manga, he is the manager of the first Card Capital store. He is knowledgeable about the Cardfight!! Vanguard card game, and teaches customers new to the game when he is available. He acts Team Q4's coach during the Japan National Tournament and VF Circuit.
In the Cardfight!! Vanguard G anime, he is now the manager of the Card Capital 2 store. It is revealed that he is a seasoned Vanguard fighter, and that he was previously part of a Vanguard team, Team Nippon, alongside Mark Whiting and Chrono Shindou's father, Rive Shindou. He uses a Murakumo deck.
Shin is Misaki's uncle and her guardian, following the death of her parents 10 years prior to the beginning of the Cardfight!! Vanguard anime and manga. At the time of his brother and sister-in-law's deaths, he was shown to be a wearing the school uniform of Hitsue High School, indicating that he may still have been a high school student. He then took on Misaki, the family pet cat, and the Card Capital store, which Misaki would later inherit.
During the Cardfight!! Vanguard anime, Shin is the manager of the Card Capital store. He played a key part in both Aichi Sendou and Misaki's growth, and in the formation of Team Q4, for which he held a qualification tournament. While he is not shown to cardfight on-screen, he is knowledgeable about the game, and is eager to participate, both by teaching new customers how to play, or by spectating games going on in the store. While he coached Aichi on the basics of the game, he later acted largely as a friend and moral support to Team Q4. He accompanied and made travel arrangements for the team, during multiple regional qualifiers and national tournaments. He once arranged a training camp in collaboration with Team Caesar, allowing the two teams to deck build and train with each other, with the specific goal of getting the relative newbie Aichi to come into contact with a larger number of more experienced players. He also accompanied the team on the VF Circuit. During the invasion of Link Joker, he was one of the few individuals who were aware of the situation, and managed to remain unaffected, providing travel and a safe haven to Aichi and his friends.
During the Cardfight!! Vanguard G anime, Shin is the manager of the Card Capital 2 store, and he divides his time between both it and the first store. As before, he gives advice to the players at his store, both in the game and morally. He takes a particular interest in Chrono Shindou, the sole user of the Gear Chronicle clan. He is revealed to have been former Vanguard teammates with Mark Whiting, and Chrono's (presumed) late father, Rive Shindou. When Chrono is considering whether or not to continue playing Vanguard, after hearing of the game's involvement in his father's disappearance, Shin fights him with his Murakumo deck, encouraging the boy to make his own decisions about what he wants to do. Shortly after, he meets with Chrono's aunt, Mikuru Shindou, to discuss Chrono's intention to continue playing Vanguard, also revealing them to know each other, and to have last talked ten years prior, before Rive's dissappearance.
Shin's role is lessened in the manga, where the tournament arc doesn't take place. However, he appears to act as an emotional pillar for Misaki, attempting to get his cold niece to open up to others, and is instrumental in arranging her fight with Aichi.
Shin is a cheerful, approachable fellow, who is enthusiastic about the game, offering to teach new players, and envying others when he can't spectate the games going on due to his workload. He is shown to be very invested in Team Q4, treating Misaki and her friends as his own friends and responsibility, willingly (but comedically bemoaningly) paying out of pocket for travel and often food during remote tournaments. He cares and thinks deeply about Misaki and her late parents, fervently attempting to make up for what the latter didn't have a chance to do.
He is shown to exercise some degree of cunning in how he helps those around him. He reintroduces Misaki to Vanguard, with the purpose of encouraging her to open up and overcome the trauma she associates with the game. He also withholds from Chrono his knowledge of the boy's family situation, while encouraging him to make his own decisions, uninfluenced by the past.
- Shin's age is a point of confusion among fans. While he is officially stated to be 38 years old at the start of Cardfight!! Vanguard: Season 1, he is shown to have been wearing Hitsue High School's uniform at the time of Misaki's parent's death, which occurred only 10 years prior. This would have made him a 28 year old high school student.
- Shin has multiple pairs of spectacles: the reflective, thick-rimmed pair he usually wears, and a non-reflective, rimless pair, which he wears while cardfighting.
- While Shin doesn't cardfight once in the first Cardfight!! Vanguard series, he does in Cardfight!! Vanguard G.
- As of GC Episode 15: Mikuru Shindou, Shin left an impression that he has a crush on Mikuru Shindou.