Gozu, originally named Toshiaki Gozu, is the central protagonist of this story, a man whose life took a dark turn before being abruptly ended by a gunshot wound. His past is marked by a rebellious and aggressive nature, having punched his father and run away from home as a young man. To survive, he dove into a dangerous underworld, consorting with criminals who paid for the company of youth, eventually securing a place for himself through sheer force of will. Gozu's upbringing was strict, with his parents completely prohibiting him from playing video games, forcing him to only watch others play at cram school. This made his childhood fascination with a particular fantasy RPG all the more intense, especially with its final boss, the Demon King Evelogia. He admired this character for fighting proudly and alone, unloved by anyone, a stark contrast to the game's hero whom Gozu despised for his self-righteous stance in killing the Demon King without a second thought. This deep-seated resentment for societal hypocrisy and his admiration for defiant strength defined his worldview long before his reincarnation.

Upon dying, Gozu finds himself reincarnated into the world of that very video game. Instead of a grand entrance as a hero, he awakens as a minor, unnamed background character, an assassin hired to kill a young version of the Demon King Evelogia. Recognizing his surroundings and realizing what has happened, Gozu feels a surge of excitement rather than fear. He immediately abandons his given mission, choosing instead to protect and support the youthful Demon King, whom he affectionately calls Eve. Gozu's personality is bold, brash, and aggressive, unafraid of violence and possessing a reckless disregard for his own safety. He is a man of raw impulse and intense passion, which is most evident in his overwhelming lust and open sexuality, feeling no shame or restraint even when their intimate moments are interrupted by others. He is direct and confrontational, quick to anger when he perceives injustice or cruelty, particularly when directed at Eve. When Eve's own parents speak of killing him out of love for the village, Gozu explodes with fury, dismantling their excuses and refusing to let them push their problems onto his charge.

Gozu's primary motivation is his deep, unwavering love and devotion to Eve, which translates into a powerful desire to protect him and alter the game's tragic storyline. He is driven by a hatred for a world that would create a hero destined to kill the last boss and sees his second chance as an opportunity to defy that predetermined fate. He is determined to use his knowledge of the game's events, recalling details from strategy guides, to prevent Eve's original turn to darkness, the deaths of his allies, and ultimately, his defeat at the hero's hands. In the story, Gozu acts as a narrative disruptor and a guardian. He is no longer a passive background element but an active force that changes the plot's course from the very beginning. His role is to be Eve's protector, confidant, and lover, pushing the shy and apologetic young Demon King to embrace his power and his destiny to destroy the world, which they jokingly refer to as their pre-wedding vacation. He constantly reaffirms his support, telling Eve that power is what wins in the end and that he should never apologize for his strength.

Gozu's key relationships are centered almost entirely on Evelogia. His bond with Eve is all-consuming, evolving from fanatical admiration to a fiercely protective and passionate romance. He is the one person who sees the Demon King not as a monster to be slain but as an individual worthy of love and devotion. He is possessive and jealous, quickly undermining anyone who he feels is getting too close to Eve or showing him affection, such as the character Mackiddie. His relationship with the rest of the world is largely adversarial, as he sees most others as hypocrites who would sacrifice an individual for their own comfort. Throughout the story, Gozu undergoes significant development, transforming from a nihilistic and violent man who had fallen to the bottom of society into a person with a clear and passionate purpose. Reincarnation and meeting Eve give him a new lease on life, allowing his capacity for loyalty and love to overshadow his past cynicism. He begins to plan for the future, thinking about how to secure artifacts before the hero and worrying about his inability to read the world's script, showing a pragmatic and strategic side to his personality. As a notable ability, Gozu relies almost entirely on his physical prowess and brawling skills, choosing to fight with his fists rather than rely on the magical weapons of this new world, which can be easily taken away. His strength and aggressive combat style are his primary tools, and he is more than willing to use them to carve a new path for himself and the Demon King he loves.