Kan Ki, known by epithets such as The Beheader, is a former bandit who rises to the rank of Great General of Qin. His early life remains largely mysterious, but it is known that he was found near death on a mountain road around the age of thirteen by a group of vagabond children who would become the Saki Clan. This clan of outcasts took him in, and he in turn transformed them from a group of weaklings into brutal survivors. After the death of his lover, Shio, at the hands of a local lord, Kan Ki exacted a horrific revenge by personally beheading every person in the lord's castle, an act that earned him his fearsome moniker. He eventually formed his own bandit gang, the Kan Ki Clan, which became the largest and most powerful in southern Qin, known for its ferocity and unorthodox methods.

In terms of personality, Kan Ki is almost always depicted with an arrogant smirk, speaking in a crude and often sarcastic manner. He exhibits a strange and dark sense of humor, once explaining that he promoted an incompetent soldier to a high rank simply because it was funny. Beneath this demeanor lies an extraordinarily brutal and ruthless individual. He has no qualms about slaughtering surrendered soldiers or civilians, routinely ordering the massacre of entire populations to achieve his goals. He employs extreme psychological warfare, such as sending mutilated corpses and bags of eyeballs to enemy camps to shatter their morale. He is also highly sadistic, taking pleasure in toying with defeated enemies, offering false hopes of survival before killing them in a humiliating fashion.

Despite this savagery, Kan Ki possesses a strikingly cool and fearless demeanor, rarely showing panic even when his own life is in danger. While he claims to be motivated by the thrill of warfare, those closest to him, like his strategist Ma Ron, assert that his true driving force is a deep, burning rage against the world. This rage stems from witnessing the elite's systemic oppression of the common people, whom he believes are complicit through their passive indifference. He holds no loyalty to the concept of states or kingdoms, viewing them as corrupt cesspools, and famously stated he did not care if Qin itself fell during the Coalition Invasion. Yet paradoxically, he exhibits genuine charisma and concern for his inner circle, whom he regards as family. He showed notable, if limited, loyalty to his former superior, the late Great General Mou Gou, saluting him in battle and honoring his memory by sacrificing captured enemies.

Kan Ki's role in the story is that of a chaotic and unpredictable, yet undeniably brilliant, military asset for Qin. He first serves as a vice general under Mou Gou before becoming an independent Great General and eventually being appointed as the fifth member of Qin's new generation of Six Great Generals. His key relationships are primarily with his own army, which is composed of various bandit clans bound by a familial loyalty to him. His inner circle includes trusted commanders like Rai Do, Koku Ou, and Ma Ron, as well as the Saki Clan, whom he considers his true family. He shares a complex dynamic with his contemporary, Ou Sen, another unconventional genius whom he fought alongside under Mou Gou. His interactions with the protagonist, Shin, often put Shin's ideals to the test, as Kan Ki openly mocks the hypocrisy of Qin's king and his dream of unification through slaughter.

Throughout the series, Kan Ki's development is revealed through glimpses into his tragic past, which reframes his monstrous actions as the product of profound loss and disillusionment. His arc culminates in a campaign into northern Zhao against his greatest foe, the legendary General Ri Boku. After one of his closest commanders is killed, Kan Ki prioritizes vengeance over strategy, leading his army into a trap. Surrounded and with all his subordinates dead, Kan Ki displayed immense willpower, fighting to the very end despite being impaled by multiple spears. He died after a final, desperate charge to kill Ri Boku, his sword breaking just as he was about to strike the fatal blow.

Notable abilities include his tactical genius, specifically his mastery of unorthodox guerrilla warfare, deception, and psychological manipulation. He excels at hit-and-run tactics, using terrain to his advantage, and infiltrating enemy lines in disguise. His strategies often involve high-risk gambles, such as using his own soldiers as bait to lure enemy commanders into a false sense of security, a tactic deemed insane by other generals. Beyond his command skills, he is a formidable and fearless fighter in his own right, possessing the strength and willpower to cut down waves of enemy soldiers even while suffering fatal wounds.