Mitch, known in the original Japanese as Mitsuhiko Tsuburaya, is a first-grade student at Teitan Elementary School and a core member of the amateur detective group called the Detective Boys. He becomes involved with the group shortly after Conan Edogawa transfers into his class, when his classmates Ayumi and Genta drag him along to investigate a supposedly haunted mansion. After that case and a subsequent treasure hunt, Mitch joins Ayumi and Genta in forming the Detective Boys. Mitch comes from a family of teachers: both his parents are educators, and he has an older sister, Asami, who is about ten years his senior. His upbringing by strict, formal parents has shaped his polite and respectful manner, leading him to address adults and even close acquaintances with formal honorifics.

Mitch is intelligent, well-read, and naturally drawn to science and technology. He enjoys studying scientific, historical, and general subjects for his own interest, and he believes that technology can solve most problems. This intellectual curiosity makes him the most logical and often the most prepared member of the Detective Boys. He frequently brings a notebook to case sites, anticipating that something important might need to be recorded. When Conan and Haibara are not present, Mitch often steps up to lead the group, using his deductive skills and factual knowledge to help solve mysteries. Despite his sharp mind, he remains a typical child who enjoys activities like making snowmen and treasure hunting, and he has a well-known dislike for carrots, usually saving them for last or leaving them uneaten.

Mitch’s primary motivation is to help others and to prove himself as a capable detective. He takes pride in his knowledge and feels rewarded when his studies prove useful. He is also deeply loyal to his friends, especially Ayumi and Haibara. He has had romantic feelings for Ayumi since kindergarten and later develops similar feelings for Haibara after she joins the group. In the case involving fireflies, Mitch ventures into a forest alone to catch fireflies for Ayumi and Haibara after hearing them express admiration for the insects, ultimately being captured by an escaped serial killer. His dedication to protecting his friends is also evident in a non-canon movie where he catches Haibara after she falls from a car, vowing never to let her go.

Within the story, Mitch serves as the third-in-command of the Detective Boys, often providing rational observations and practical solutions when the others are stuck. He is a supporting character whose contributions help Conan solve cases, though he is usually unaware of Conan’s true identity. His key relationships include his close friendship with Genta, his crushes on Ayumi and Haibara, and his respect for Conan and Professor Agasa, whom he calls “Professor.” He also holds formal interactions with police officers and other adults.

Over the course of the series, Mitch demonstrates noticeable development. He becomes more resourceful and brave, taking initiative in dangerous situations. For example, when trapped in a cave with Conan unconscious, he solves the riddle to find the exit. When Haibara sprains her ankle while being pursued by a murderer, Mitch carries her to safety and leaves a coded signal using a method Conan taught him. He also occasionally acts as a leader when Conan and Haibara are absent, using his intelligence to guide the group. His growth is marked by a growing confidence in his own abilities and a deeper sense of responsibility toward his teammates.

Notable abilities include his scientific reasoning, his habit of preparing for any scenario by taking notes, and his basic knowledge of first aid and signaling techniques. He is also a quick thinker in puzzles and code-breaking, often arriving at solutions before his peers. While his deductions are not always correct, his ability to learn from each case and his eagerness to apply what he has read make him a valuable and steadily improving member of the Detective Boys.