Mitsuhiko Tsuburaya is a first‑grade student at Teitan Elementary School and a founding member of the amateur detective group known as the Detective Boys. He first becomes involved with Conan Edogawa, Ayumi Yoshida, and Genta Kojima when they investigate a supposedly haunted mansion and later search for a cache of stolen gold coins. After those early adventures, Mitsuhiko joins Ayumi and Genta in forming the core of the Detective Boys, a group that regularly stumbles into criminal cases and helps solve them.

Mitsuhiko comes from a family of teachers; both his parents are educators, and he has an older sister about ten years his senior. This upbringing gives him a notably polite and formal manner of speaking, especially toward adults and older individuals, as he habitually uses respectful suffixes such as “‑san” in Japanese regardless of how close he is to the person. Despite his formal exterior, Mitsuhiko is a curious and well‑read child who enjoys studying science, history, and general knowledge for his own interest. He often approaches problems with a scientific mindset and a belief that technology can solve most challenges. He likes to be prepared for any situation and frequently plans ahead—for example, taking notes on codes during an investigation because he anticipates they might later become important evidence. When Conan and Ai Haibara are not present, Mitsuhiko often steps up as the most intellectually capable member of the group, showing sharper reasoning and quicker thinking than Genta or Ayumi.

At the same time, Mitsuhiko remains an ordinary elementary‑school child. He enjoys age‑appropriate activities such as treasure hunting, making snowmen, and watching movies about monsters like Gomera or superheroes like Kamen Yaiba. He has a mild dislike for carrots and tends to eat them last if at all. His motivations are largely driven by a genuine love of learning and a desire to help his friends. He feels rewarded when his knowledge impresses others, such as when Ayumi comments on his accurate historical facts about a landmark in Kurashiki.

Within the Detective Boys, Mitsuhiko serves as the third‑in‑command behind Conan and Haibara, but he frequently acts as the operational leader when the two more experienced members are unavailable. His role in the story is that of a loyal and resourceful sidekick who grows in confidence and deductive skill over time. He has been shown to solve riddles that trap the group, apply first‑aid techniques learned from Conan, and leave coded messages to signal his location when in danger. His proactive thinking and attention to detail often provide crucial clues for the police.

Key relationships shape his character. He is close friends with Ayumi Yoshida and Genta Kojima, having known them since preschool or kindergarten, and he shares a lighthearted rivalry with Genta for Ayumi’s attention. After Ai Haibara joins the group, Mitsuhiko develops romantic feelings for her, which become evident during an incident where he cares for her after she sprains her ankle and carries her to safety. He also holds deep admiration for Conan, though he is unaware of Conan’s true identity as Shinichi Kudo, and he often learns practical skills from him. Outside the group, Mitsuhiko treats adults such as Professor Agasa, detectives like Takagi and Sato, and other characters with consistent politeness.

Mitsuhiko undergoes noticeable development throughout the series. He becomes more confident in his own abilities, sometimes taking the lead in investigations and even venturing out alone to catch fireflies for Ayumi and Haibara, an adventure that brings him face‑to‑face with a dangerous fugitive. His deductive reasoning improves steadily under Conan’s indirect guidance, and his willingness to act independently shows his growth from a hesitant participant to a capable young detective. Despite his increasing competence, he retains a childlike vulnerability and occasionally misjudges danger, reminding the audience that he is still learning.

Notable abilities include his extensive general knowledge, a methodical and analytical approach to puzzles, and a talent for remembering and applying scientific facts. He is also skilled at using the Detective Boys’ gadgets, such as the radar badge and voice‑changing glasses, and he has demonstrated basic first‑aid knowledge. His forward‑thinking nature and habit of documenting clues make him an asset in unraveling mysteries, especially when he is the one to notice overlooked details or piece together historical references.