Natsuhiko Hyūga attends Kamome Academy as a second-year student and belongs to the Broadcasting Club. Outwardly, he appears friendly yet shallow, though his true motives and loyalties shift ambiguously. He possesses notably good looks, featuring short, messy red and black hair in an undercut and grey eyes. His standard uniform is modified: the shirt hangs unbuttoned with sleeves rolled up to reveal a teal long-sleeved undershirt. He wears a germanium necklace on a red cord, a gift from Sakura Nanamine, alongside a separate black sports necklace. His personality blends recklessness with obsessive loyalty. Primarily allied to Tsukasa Yugi and Sakura due to persistent romantic feelings for the latter, he interprets Sakura's consistent coldness as "special treatment," remaining undeterred. Willing to deceive or endanger others for Sakura's goals—like manipulating Nene Yashiro into peril—he nonetheless shows contradictory protective instincts. During an escape with Nene, he insisted on opening doors to shield her and urged her onward when he could no longer proceed. However, he demonstrates ruthlessness, casually rationalizing acts like killing Mitsuba Sousuke and poisoning the Clock Keepers' Big Clock. A critical secret is his nature as an immortal human. No physical harm can kill him, and his blood proves lethally toxic to supernaturals. Weaker entities disintegrate instantly upon contact; stronger ones like Hanako suffer severe burns. This trait ensures his survival in fatal situations, such as supernatural captivity or fire attacks. He weaponizes this ability strategically, once coating the entire Big Clock in the Sealed Auditorium with his blood. This act threatened the Clock Keepers' destruction and directly caused time at the school to stop, facilitating the "New Present" timeline. His relationships center on devotion to Sakura and collaboration with Tsukasa. He performs Sakura's tasks without hesitation, viewing them as chances for closeness. Within the Broadcasting Club, he participates in schemes disrupting the school's supernatural balance, often acting as an antagonist to the protagonists. His dynamic with Nene remains complex: complicit in endangering her yet assisting her in crises, indicating no personal malice. Personal details include hobbies like fishing—where he boasts of catching "mullets and sometimes girls"—and karaoke, displaying skill at singing and dancing to idol songs. He works out regularly, is startled by lightning, and favors black soybean senbei as a snack. His latest noted concern is annoyance with Tsukasa's behavior.