Mitsuhiko Tsuburaya, a first-grade student at Teitan Elementary School, is a founding member of the Detective Boys, united through their investigation of a haunted mansion hiding an unsolved homicide. Raised by schoolteacher parents who instill formal speech and politeness, he consistently uses honorifics like "-san" and maintains a respectful manner. His older sister, Asami Tsuburaya, is a decade his senior.

Driven by logical reasoning and scientific curiosity, Mitsuhiko approaches mysteries methodically, anchoring conclusions in empirical principles. Though physically average for his age, his athleticism exceeds that of peer Genta Kojima. His advanced grasp of electronics and deductive techniques occasionally impresses even older allies. When Conan Edogawa or Ai Haibara are unavailable, he naturally steps into leadership, directing the group’s investigative efforts.

Interpersonal tensions arise from his longstanding kindergarten crush on Ayumi Yoshida and later fascination with Ai Haibara, complicated by awareness of Ayumi’s feelings for Conan. His earnestness sometimes veers into overconfidence, yet childlike credulity surfaces in his belief in fictional monsters or supernatural lore.

Notable moments showcase his growth: independently unraveling Sherlock Holmes-inspired fraud schemes, decoding a teapot’s cipher to expose a robber’s escape plan, challenging flawed postal evidence, and bravely shielding Ai during peril. Across films, OVAs, and episodes, he aids in thwarting bomb plots, art thefts, and historical enigmas, evolving from a cautious skeptic to a self-reliant investigator. His name—combining "light" and "lad"—mirrors his role as the group’s intellectual spark, illuminating paths through curiosity and resolve.