Tatsuya Tachibana is a main character of Cardfight!! Vanguard: Shinemon. He is a transfer student in the same class as Mikuru Shindou at Tokyo Metropolitan Harumi Middle School. Starting out as a commrade for Shinemon, after a two year skip, he becomes a researcher for Ryuzu Myoujin to further his own goals, becoming an antagonist for the second half of the arc.
He looks up to Shinemon Nitta, and tries to improve himself to be more like Shinemon. He tends to be serious and honest. However, after the incident at Yumigatake, his personality suddenly turned antagonistic, doing whatever it took to achieve his goals, including working with Ryuzu Myoujin and betraying him as well as taking Chrono hostage.
He wears a purple school uniform, with matching jacket and slacks. His hair is grey and mostly falls down around his head except for one large spike. His eyes are a deep purple.
After two years, he became a researcher for the Unit Summoning Project and wore a standard lab coat.