Ayumi Tachibana is one of the main characters in the Famicom Tantei Club franchise. In the first two games, she is the partner of the unnamed main character, but in BS Tantei Club: Yuki ni Kieta Kako she takes on the role of the main character. Her story begins in Famicom Tantei Club Part II: Ushiro ni Tatsu Shoujo, which is the prequel to the first game, Famicom Tantei Club: Kieta Koukeisha. Ayumi also appeared as a trophy in Super Smash Bros. Melee, which explains that she is a part of the Famicom Detective Club (as it would be translated into English).
Ayumi also made a brief appearance in the Japanese version of WarioWare: Touched!, appearing in one of 9-Volt's games based on Famicom Tantei Club: Part II.
In Famicom Tantei Club Part II, the 15-year old Ayumi is not yet part of the detective club, but rather is enrolled at Ushimitsu High School, the pivotal location throughout the events of the game. She was best friends with the first murder victim, Yoko Kojima, who also attended Ushimitsu. Ayumi is a very important witness, as well as a great help to the unnamed main character during the course of the game. At the end of the game, she makes the decision to join the detective agency that the main character and Shunsuke Utsugi (a private detective) operate.
In the first game, Famicom Tantei Club: Kieta Koukeisha, Ayumi assists with the investigation in a variety of ways. She is 17-years old in the game.
Ayumi takes over as main character in BS Tantei Club, where she returns to her parents' home in the Ochitani village. She came to visit her mother, Toshie Tachibana, but gets involved in a murder investigation involving the mayor of Ochitani, Gozo Kusano. Due to a long-lasting feud between the Tachibana and Kusano family, and the fact that Toshie discovered the body, Ayumi is swept up in the recent murder, a connected murder from 18 years ago, a series of serial killings, and an old ochimusha legend.