Natsuhiko Hyūga is a second-year student at Kamome Academy and a member of the Broadcasting Club. He stands out with his tall frame, messy short undercut hair blending red and black tones, and grey eyes. He typically wears his Kamome uniform unbuttoned, sleeves rolled up to show a teal long-sleeved shirt underneath. He adorns himself with a germanium necklace on a red cord, a rectangular black sports necklace, and two stud earrings. His personality mixes superficial charm with underlying ruthlessness. He projects confidence, flirtatiousness, and lightheartedness, actively seeking female attention and claiming to be a ladies' man. This contrasts sharply with his intense loyalty and obsessive devotion to Sakura Nanamine, whom he calls "Miss." He interprets Sakura's frequent coldness, insults, and physical restraint as "special treatment" or affection, displaying a masochistic enjoyment of her harshness. Though he occasionally complains about being seen as a "bad guy," he casually engages in morally questionable actions aligned with Sakura's or Tsukasa Yugi's goals, including deception, endangering others, and lethal violence against supernaturals. He demonstrates situational recklessness, like opening multiple dangerous doors during an escape with Nene Yashiro, yet also shows protective instincts, such as shielding others from immediate threats. Natsuhiko is affiliated with Tsukasa Yugi and Sakura Nanamine as part of a group aiming to destroy Kamome Academy's Seven Mysteries. His primary motivation is fulfilling Sakura's requests, often hoping to earn a date. Initially perceived as human, he is later revealed as an immortal supernatural entity incapable of dying regardless of physical harm, linked to the rumor of "the human who won't die no matter how many times he is killed." His blood is lethally toxic to supernaturals, causing rapid disintegration upon contact: stronger entities like Hanako suffer burns, while weaker ones like Mitsuba Sousuke dissolve completely. His blood exhibits autonomous properties, capable of expanding to engulf large structures like the Clock Keepers' Big Clock in the Sealed Auditorium, poisoning the school's temporal mechanism, halting time, and contributing to the "New Present" timeline. This potency stems from accumulated curses and filth from numerous deceased souls. His immortality allowed survival in hostile environments like the "Place That Is Everywhere And Nowhere," implying the demise of supernaturals who tried to harm him there. His key relationships center on Sakura and Tsukasa. His actions are driven by devotion to Sakura, executing tasks like rumor-spreading, poisoning the clock tower, and eliminating obstacles such as Mitsuba Sousuke. He tolerates Tsukasa's disruptive behavior despite finding it annoying, collaborating for their shared agenda. Interactions with Nene Yashiro show moral ambiguity; he deceives and endangers her but also guides her during escapes and expresses concern for her safety. His dynamic with Mitsuba included flirtatious remarks preceding Mitsuba's murder, highlighting his willingness to eliminate even those he finds "cute" if they impede his objectives. Notable trivia includes his hobbies of fishing and karaoke (especially idol songs), a preference for black soybean senbei snacks, and a recurring concern about Tsukasa's annoyance. He claims to catch "things that aren't fish, like girls" while fishing and works out regularly.