Tanpei serves as the primary protagonist and loyal 13-year-old lab assistant to Dr. Kieta. Characterized by intelligence, athleticism, and courage, he possesses exceptional mechanical aptitude, demonstrated by building the robot Chorobo and frequently repairing the Time Bokan machines after battles. He typically wears a blue jumpsuit and helmet featuring a stylized "T" insignia associated with Dr. Kieta's inventions.

Personality-wise, Tanpei shows determination and a strong sense of justice, though he can also be brash, cocky, and prone to panic in stressful situations. He becomes easily flustered around attractive girls, sometimes causing friction with Junko, Dr. Kieta's granddaughter. Tanpei shares a close dynamic with Junko, frequently comforting and encouraging her during missions; mutual romantic feelings exist between them, evolving over time with later sources indicating they eventually become engaged.

Beyond his mechanical skills, Tanpei is proficient in combat, capable of physically confronting adversaries and effectively piloting Time Bokan mechas. He leads a team—including Junko, Chorobo, and the parrot Parrosuke—through time in insect-shaped machines to locate the missing Dr. Kieta, contending with the Time Skeletons who pursue the powerful Dynamonds Dr. Kieta discovered. Tanpei's mechanical expertise proves crucial in modifying and repairing their time-traveling machines throughout these conflicts.

Beyond the original 1975–1976 series, Tanpei appears briefly alongside Junko in the audience during the first episode of the OVA *Time Bokan: Royal Revival*. He is also featured as a teenager in the 2008 *Yatterman* reboot series.