Unlike typical shōnen heroes who chase grand ambitions like saving the world or becoming king, Denji's goals are fiercely basic. He initially wants a warm place to sleep, three meals a day with jam on his bread, and a girlfriend. Having never attended school, Denji behaves in a vulgar, unrefined, and highly reactive. Because he lacked any parental affection or social framing, he is extremely naive and desperately craves intimacy. This makes him highly susceptible to manipulation by authoritative figures, particularly his supervisor Makima. Despite his self-centered outer shell, he shows deep, protective loyalty toward those he forms close bonds with, such as his surrogate siblings Power and Aki Hayakawa. With his best friend giving him the powers of chainsaw man being his heart

Aki initially appears cold, serious, and deeply professional. He clashes with Denji early on, viewing his chaotic nature and simple motives as a mockery of devil hunting. Beneath his aloof mask, Aki is arguably the most sensitive member of his squad. He forms deep attachments quickly and secretly weeps for comrades lost in battle. He serves as the grounding anchor for his household. He takes on cooking, cleaning, and managing finances to keep up with the messy habits of Denji and Power.

Power is wildly arrogant, habitually declaring herself the smartest and strongest being alive. She refers to herself in the third person using the archaic Japanese pronoun "Washi" and constantly demands praise. She is completely untrustworthy, routinely shifting blame onto others (usually Denji) whenever she breaks something or messes up a mission. Having lived as a wild animal, she despises bathing, rarely flushes the toilet, refuses to eat vegetables, and throws violent tantrums when fed anything other than meat.

On the surface, Makima behaves as a gentle, soft-spoken, and highly professional leader. She uses physical affection, gentle manipulation, and empty promises of intimacy to build absolute loyalty in Denji. In reality, she views all of humanity as "dogs" or tools to be used and discarded. She possesses zero genuine empathy for her squad members, methodically orchestrating horrific tragedies to break Denji's spirit and sever his emotional anchors.