Gaku is a tall and muscular young man with spiky, slicked-back bluish-gray hair and striking hot pink eyes accented with red eyeliner at the outer corners. He wears black square-shaped earrings and a high-collared navy blue jacket with a yellow button that hangs loosely over his scarred body. His sleeves are rolled up, his hands are wrapped in bandages, and he pairs navy blue baggy pants with white sneakers that have light gray stripes and black laces, though in the manga his sneakers appear completely white. He always carries his weapon wrapped in bandages over a bag on his right arm.

After his battle with Takamura during the JAA raid, Gaku lost his right ear, parts of his left middle and ring fingers, and his entire right hand. Kashima later reattached his fingers and hand but was unable to restore his ear, leading Gaku to wear a circular patch in its place.

At the age of thirteen, Gaku had a slimmer build and wore a black tank top along with a pair of white shorts.

Gaku vs. Nagumo

Gaku is an exceptionally powerful assassin whose abilities make him one of the deadliest individuals in Sakamoto Days. He has demonstrated overwhelming strength and combat efficiency, effortlessly slaughtering hundreds of JAA members. Even more impressively, he was able to hold his own against Takamura, one of the strongest members of the Order. His immense power and relentless fighting style earned him high praise from Nagumo, who described Gaku as the strongest opponent he had ever faced.

As a master combatant, Gaku wields his massive mace with remarkable skill and precision, capable of executing devastating blows with minimal effort. His mastery in close-quarters combat is further shown through his use of a one-inch punch that delivers incredible force. Nagumo described his fighting ability as monstrous and even compared it to Taro Sakamoto’s when he was younger, emphasizing Gaku’s immense natural talent and lethal instincts in battle.

Gaku possesses extraordinary physical strength, enabling him to swing his heavy mace effortlessly, disembowel enemies with a single punch, and tear through groups of assassins without pause. While controlling Shinaya’s body, he became an unstoppable force, annihilating nearly every JCC faculty member on the island and overpowering fighters like Shin Asakura, Joichiro Kaji, Mafuyu Seba, and Nao Toramaru. His immense power allowed him to send Nagumo crashing through multiple walls with a single swing and launch him away with one punch.