Hachisuka Kotetsu is an uchigatana, a type of sword, brought to life as a touken danshi within the citadel. His historical counterpart was forged in 1665 by the renowned smith Nagasone Okisato and was a treasured possession of the Hachisuka clan, from whom he derives his name.

Hachisuka carries himself with an air of undeniable beauty and flawless style. His most defining personality trait is his profound pride in being an authentic Kotetsu blade, a genuine article amidst a sea of counterfeits. This pride directly shapes his key relationships. He is very fond of his younger brother, Urashima Kotetsu, whom he accepts as a fellow genuine sword. Conversely, he openly protests and maintains a strained relationship with Nagasone Kotetsu, as he considers Nagasone to be a fake. This dynamic is central to his interactions, creating a consistent source of tension and conflict within the group. Despite his outward rejection, there are suggestions that he is secretly drawn to Nagasone's competence and rough nature, though he is reluctant to admit it.

Within the daily life of the citadel, Hachisuka participates in the routine chores and missions. In one instance, he is assigned to cleaning duty and later complains about an excess of cardboard boxes, seeking permission to discard them. This shows his practical, if slightly fastidious, side.

Physically, Hachisuka is recognized by his long purple hair and blue eyes. His design incorporates elaborate golden armor and accessories, a stylistic choice that mirrors the actual golden-colored mountings (koshirae) of his original sword form. His abilities as a touken danshi are typical of his uchigatana class, making him a capable fighter in the historical battles the swords are sent to protect. Over time, his experiences and interactions, particularly the underlying tension and reluctant respect for Nagasone Kotetsu, contribute to his character development, though his fundamental pride in his authenticity remains a core aspect of his identity.