Mitsuhiko Tsuburaya is a student in Teitan Elementary School when Shinichi joins his class as Conan Edogawa. Shortly afterwards, his classmates Ayumi and Genta have the idea of investigating an apparently haunted mansion, and they persuade Conan to come along. When Mitsuhiko expresses his skepticism about supernatural hauntings, Genta forcefully 'persuades' him to tag along as well. As it turns out, the ghost story is a cover-up for an old homicide case.

Soon after, the accidental acquisition of a treasure map leads Ayumi, Genta, Mistuhiko and Conan on a hunt for a cache of stolen Italian gold coins, during which Conan saves them from getting killed by the mafia members who are also after the gold. After the case is resolved, Mitsuhiko joins Genta and Ayumi in forming the nucleus of an amateur detective group, the Detective Boys.

Mitsuhiko enjoys reading science books and takes a scientific approach to problem-solving. He is a smart and well-read first-grader who believes that technology can solve most problems. Due to his strict and formal upbringing by his parents, he tends to be very formal towards his elders, addressing them (in Japanese) with the formal suffix "-san" without regard to the intimacy of their relationship.

It has been shown at numerous times that Mitsuhiko really likes to be prepared for any occasion. He enjoys studying scientific, historic and general subjects for his own interest and fun. This eventually allows him to provide useful insights whenever necessary. He's been (or felt) rewarded a few times for his knowledge. In one instance, Ayumi said how impressed she was after Mitsuhiko provided some precise historical facts behind the Ohashi House in Kurashiki, and he thought to himself with a big happy smile on his face: "I'm so glad I studied!".

One of his other qualities is that he tends to be proactive in many situations and thinks ahead to possible outcomes. For example, while the Detective Boys were trying to solve riddles they found in a Momotaro container in a small river in Kurashiki, a murder occurred which eventually led to the different codes to get burned. Conan, knowing that resolving those codes would lead to concrete proof as to who the murderer might be, was quite pleased when Mitsuhiko proudly announced that he took notes in his Detective Boys notebook "thinking that something like that could happen". He has often been shown as shrewder and more quick-witted than Genta and Ayumi, sometimes leading the investigation when Conan and Haibara aren't present.

Despite the preciousness of his intelligence, Mitsuhiko remains an elementary school child, and enjoys activities of his age, such as making a snowman or treasure hunting. As a consequence, he is best friends with Genta and Ayumi. Mitsuhiko has a dislike for carrots, and will always eat them last _(if ever)_ if he can help it. Both of his parents are both teachers, and he has an older sister, Asami Tsuburaya, about ten years his senior. Mitsuhiko doesn't like to eat carrot but be careful.

(Source: Detective Conan World)