Kazuya Misaki is a support member of the Nozama Peston Service, the extermination team that hunts dangerous Amazon creatures. Before joining the team, he worked as a con artist and chose to become an exterminator to pay off significant debts, particularly to a frightening criminal syndicate. His age is 35 during the events of the first season, later progressing to 42 by the time of The Last Judgement.

Within the often grim and violent context of the team's mission, Misaki stands out as the most cheerful and jovial member, frequently seen smiling and making jokes. He is an affectionate man, giving his teammates nicknames; he refers to Mamoru as Mamo-chan and Haruka as Darling Boy. This warmth defines his key relationships. His bond with Mamoru is especially strong, as he acts as a kind of emotional anchor for the young Amazon. This devotion is profoundly tested when Mamoru, overtaken by cannibalistic instincts, eats Misaki's left forearm. Even after this traumatic event and having his arm replaced with a prosthetic, Misaki refrains from shooting Mamoru, demonstrating the depth of his care.

His primary role in the extermination team is to manage the public during missions. Using his skills as a former swindler, he is a master of conversation and distraction, responsible for diverting the attention of onlookers to ensure the team's operations remain secret and that civilians are kept out of harm's way. He is typically armed with firearms, having been seen using a shotgun and a submachine gun in his duties.

Throughout the series, Misaki's development is tied to his personal struggles and his evolving sense of duty. He continues his dangerous work with the team even after losing his arm, driven partly by the need to repay his debts, which he slowly manages to do. His journey leads him to The Last Judgement, where he continues to fight alongside his comrades.