Hugo, originally named Natsume Kengo in his past life, was a Japanese high school student who commanded classroom respect with a frank and egotistical personality. His childhood friend, Issei Sakurazaki, understood him deeply and moderated his behavior. Reborn as the crown prince of the treacherous Renxandt Empire and isolated without Issei's influence, Hugo's personality warped. Seeking to regain social dominance, he enrolled at Analeit Kingdom Academy but grew fiercely envious as his classmate Shun became the center of attention among their reincarnated peers. This resentment culminated in a failed assassination attempt against Shun during a mountain excursion. As punishment, their former teacher Filimøs, reincarnated as an elf, used her Ruler authority to strip Hugo of his unique skill, Emperor, and most of his stats and abilities, confining him to house arrest. This event became Hugo's breaking point, fueling his descent into vengeance-driven madness.

Driven by hatred, Hugo allied with the demon Lust, hypnotizing key figures like Prince Cylis Analeit, Princess Sue Analeit, Saint Yuri Ullen, and Katia to manipulate them into supporting a coup against the Analeit Kingdom. He framed Shun for the king's murder, declared himself the new Hero, and blamed the elves for the conflict. Leading a coalition of human nations, he invaded the Great Garam Forest to destroy the elf village.

During the battle, Hugo confronted Shun and Filimøs. Though initially overpowering Filimøs, he was thwarted by Sophia Keren's intervention. After Shun saved Filimøs, Hugo dueled Shun and was defeated. When Hugo begged Sophia for aid, she revealed she had only used him to instigate the elf battle before discarding him. Enraged by this betrayal, Hugo attacked Sophia but was effortlessly defeated.

Hugo's capabilities evolved significantly after losing his Emperor skill, which had boosted his stats and inflicted fear on opponents. He acquired two Ruler skills: Lust, granting permanent mind-control abilities, and Greed, allowing him to absorb a fraction of his victims' stats and skills upon killing them. These skills enabled his rapid resurgence. To compensate for his unbalanced build, he wielded high-grade equipment like Dragon Armor crafted from monster materials and a broadsword. He retained the passive skill n% I=W, common to all reincarnations, which restored his health, mana, and stamina upon leveling up.

Hugo's relationships centered on animosity and manipulation. He harbored indiscriminate hatred toward Shun due to their clashing personalities and Shun's perceived theft of his spotlight. His interactions with Filimøs deteriorated from disrespect to murderous loathing after she removed his powers. He viewed Sophia as a tool, demeaning her despite her strength, unaware she exploited him for her own goals. His connection to Yuri was pragmatic, leveraging her position as the Saint for his coup. The absence of Issei, who died in the new world, was cited as a critical factor in Hugo's corruption, as his presence might have prevented Hugo's downfall.