Kazumu Tamaki is a character appearing in the Modern Era arc of To Your Eternity. He is an eighth-grade student at Minamoto Junior High School and a member of the school's Occult Research Club, where he considers himself the self-appointed brawn of the group. At the beginning of the Modern Era arc, he was a seventh grader.

Physically, Kazumu has a build that contrasts sharply with his clubmate Suzuhiko. He has a round torso with thick limbs. His black hair is cut short with short sideburns, and his fringe is shaped into a vague triangular point. He has short, round eyebrows, each featuring a distinct cut that makes them resemble lily pads. His typical attire includes dark trousers and a camouflage shirt, accessorized with a dog-tag necklace and two black stripes painted on his cheeks, giving him a somewhat ruffian appearance.

Despite his tough exterior, Kazumu's personality does not align with a love for violence. He has been observed lifting weights in the club room, indicating a genuine interest in physical fitness and health, which may also stem from an aspiration to become a soldier. When he does resort to physical action, such as slapping his clubmate Yuuki, it is with the intention of stopping what he perceives as dangerous delusions, specifically concerning the immortal being Fushi.

His primary role in the story is as a supporting character within the modern-day setting, interacting with Fushi and the other students at his school. His key relationships are with his fellow members of the Occult Research Club, including Yuuki and the club's brains, Suzuhiko, who is a computer expert. Kazumu's most notable ability is his physical strength, which he actively develops and serves as his main contribution to the group.