Naofumi Iwatani, a 20-year-old university student from Japan, immersed himself in otaku culture—video games and light novels. Witnessing parental pressure strain his younger brother, Naofumi intervened by introducing gaming as stress relief, ultimately mending their family bonds. This period also unveiled an unusual natural affinity, as wildlife consistently displayed marked friendliness toward him. His journey to another world began when he discovered the book "The Record of the Four Holy Weapons" in a library, transporting him to Melromarc. There, he was summoned as one of the Four Cardinal Heroes, wielding the Legendary Shield. Initially trusting and optimistic about his heroic duty, Naofumi's personality shattered after betrayal by Princess Malty Melromarc. Her false accusation of sexual assault plunged him into financial ruin, widespread hatred, and social isolation. This forged intense cynicism, distrust, and a permanent undercurrent of hostility, concealed beneath a calm exterior. Convinced only a slave curse could prevent further betrayal, he purchased the demi-human child Raphtalia. He later acquired a Filolial egg that hatched into Filo. Though treating both pragmatically at first, Naofumi gradually formed paternal bonds, nursing Raphtalia through illness and training her in combat. These relationships sparked slow emotional healing, though deep-seated difficulty with intimacy and trust persisted. Combat for Naofumi centered entirely on the Legendary Shield, offering exceptional defense but no innate offense. The shield absorbed materials to unlock new forms, granting skills such as the deployable "Air Strike Shield" or the trapping "Shield Prison," forcing reliance on allies for attacks. Extreme rage could trigger the "Shield of Wrath," a cursed form countering assaults with dark flames at the cost of mental corrosion and temporary stat reduction. Ostracism honed his self-sufficiency into merchant and crafting expertise, enabling the creation of potions, accessories, and armor like Barbarian Armor +3. He utilized support magic, including healing and stat boosts, and employed "Hate Reaction" to draw enemy focus. Naofumi evolved into a pragmatic leader. Queen Mirellia's aid cleared his name, leading to his governorship of Lurolona Village. He repopulated it by purchasing and freeing enslaved demi-humans, treating them more like family than servants. His strategic acumen shone during crises, uniting armies against threats like the Spirit Tortoise and the Phoenix, often correcting or assisting the other Cardinal Heroes despite mutual animosity. He maintained a reputation for underhanded tactics, manipulating slave contracts for growth benefits and humiliating foes—renaming Malty and her father with derogatory epithets. His tendency to "reflect" others' treatment back at them was mirrored when chosen as the Vassal Mirror Hero in another world. Later developments saw Naofumi balancing cynicism with protective instincts. He remained oblivious to romantic advances, particularly from Raphtalia in her adult form, viewing her as a daughter. Post-Spirit Tortoise, his focus shifted to preparing for escalating Waves of Calamity while rebuilding societal equality in Melromarc. His appearance in Isekai Quartet 2 involved interactions with characters from other isekai series, consistent with his established traits and dynamics.