Kazunori Negishi is a young man from a rural farming community who moves to Tokyo with a pure and gentle dream of becoming a pop musician. His personal taste is the antithesis of heavy metal; he adores sweet, romantic Swedish pop music and aspires to write and perform cheerful love songs. However, his reality is a harsh and ironic contradiction. He finds himself as the frontman, vocalist, and guitarist for the immensely popular underground death metal band Detroit Metal City, performing under the stage name Johannes Krauser II.

In his everyday life, Negishi is timid, shy, and conflict-avoidant. He is presented as a somewhat nerdy and unassuming individual with a slightly awkward demeanor who wishes only to live a peaceful life and avoid trouble. He is profoundly embarrassed by his involvement in death metal, which he personally hates, and is desperate to keep his true identity hidden from those he cares about, especially from the girl he loves who despises his band. Despite his revulsion for the genre, he is not a passive victim of circumstance but is portrayed as remarkably talented at it, a fact that traps him in a cycle of professional success and personal misery.

The core of Negishi's character is his duality, which exists on a spectrum rather than as a true split personality. He is fully aware of his actions, and his transformation into Krauser II is often a deliberate, if reluctant, performative switch. While in character, he becomes a vulgar, violent, and misogynistic demon who speaks in a deep growl and performs acts of simulated destruction and debauchery on stage. This persona sometimes emerges during moments of extreme stress or anger, where he channels his frustration into the monstrous character, often with unintended and extreme consequences. The series derives much of its humor from the contrast between his gentle private apologies for his alter-egos actions and the over-the-top violence Krauser is known for.

Negishis primary motivation is to escape the metal scene and achieve success with his original pop music. He is driven by a desire for social acceptance and a longing for a normal life and a romantic relationship. His key relationships highlight this central conflict. His band manager is a vulgar and manipulative woman who recognizes his genuine, undeniable talent for death metal and forces him to continue performing against his will. In contrast, his love interest is a music journalist who despises Detroit Metal City, forcing Negishi to constantly construct elaborate lies to keep his two worlds from colliding. His role in the story is therefore one of relentless, and often hilarious, conflict. He is the reluctant king of a world he despises, struggling to maintain his personal identity while being celebrated for his fraudulent monstrous one.

Throughout the narrative, Negishi evolves from simply being ashamed of Krauser to a more complex acceptance of this part of his life. While he never fully embraces death metal as his passion, he learns to harness the power of his stage persona to solve problems and protect others, blurring the line between his fake demonic self and his real heroic nature. Despite this, his development is often cyclical, as he continually finds himself dragged back into the metal world just as he thinks he has escaped, highlighting the inescapable nature of his incredible, unwanted talent. His notable abilities include a stunning vocal range that allows him to produce both high-pitched pop melodies and guttural death metal growls, as well as impressive guitar skills adapted for both genres. His signature ability, however, is his astonishing stage presence as Krauser II, which is so powerful and authentic that it captivates legions of devoted metal fans and terrifies everyone else.