Kokatsu

is the father of Kawaki.

Background
In the anime, Kokatsu was apparently a former shinobi who was a hero from the Fourth Shinobi World War, though many doubted the claim given his boorish nature. Whatever hardships he had to endure ultimately took its toll on him, leaving him a bitter man who took solace in drinking. Eventually, he would have a son, Kawaki. Kokatsu was abusive towards Kawaki. One night, after locking Kawaki away for accidentally breaking his bottle of alcohol, Jigen arrives to their home to buy Kawaki from him. Kokatsu without hesitation agreed to the offer, openly disowning Kawaki and leaving his small house with his newfound profit.

Personality
In every sense, Kokatsu proved himself a shameless man who cared only about himself. An alcoholic and irritable by nature, he would take his anger out on whoever he saw fit. This ultimately became the dynamic with his son Kawaki. He would regularly abuse the boy physically, including withholding meals for the smallest of mistakes and lock him up in a room should he fail him. He also torment the boy verbally, constantly referring to his son as empty and worthless. His lack of compassion would even force Kawaki to perform various jobs around town just to keep his alcohol supply up. Ultimately, he proved how little he valued his son when gleefully sold Kawaki to Jigen and just as quickly moved on with his life without a second thought.

Trivia

 * means "drying up" or "repletion".
 * Kokatsu's name was not mentioned in the manga, only appearing in the credits of episode 192.