Hyuuga Natsuhiko attends Kamome Academy High School as a second-year student and belongs to the Broadcasting Club. He possesses immortality, rendering him indestructible regardless of fatal injuries. His blood carries extreme toxicity for supernaturals, causing instant disintegration in weaker entities or painful burns in stronger ones like the Seven Mysteries; Hanako identifies it as containing "the filth and curses of dozens of the dead." Natsuhiko has short, messy red and black hair styled in an undercut, grey eyes, and a good-looking appearance. He wears the standard Kamome boys' uniform with his shirt unbuttoned and sleeves rolled up, revealing a teal long-sleeved shirt underneath. His accessories include a germanium necklace on a red cord, a gift from Sakura Nanamine, and a black sports necklace. Outwardly flippant and flirtatious, Natsuhiko actively seeks female attention and labels himself a "bad guy." He exhibits a masochistic streak, interpreting Sakura Nanamine's cold dismissals—like ignoring him or calling him "invisible"—as affectionate "special treatment" or expressions of love. Despite this seemingly shallow demeanor, he demonstrates fierce loyalty and recklessness, particularly in his devotion to Sakura. He follows her orders without question, even when they involve endangering others or manipulating events, such as deceiving Nene Yashiro or murdering Mitsuba Sousuke. While capable of detachment, casually discarding people or causing harm to achieve his goals, he occasionally shows concern for allies like Mitsuba. Natsuhiko collaborates closely with Sakura Nanamine and Tsukasa Yugi, driven primarily by his obsessive crush on Sakura. He aids their mission to destroy the Seven Mysteries and their Yorishiro, believing Tsukasa will grant him a date with Sakura upon completion. His interactions with Sakura involve persistent advances, including attempted hand-kissing and misguided gestures like offering a love potion, consistently met with rebuffs. He views Tsukasa as an annoyance, complaining about his behavior yet continuing their partnership. Key plot actions include Natsuhiko using his cursed blood to threaten the Clock Keepers at the Sealed Auditorium's Big Clock. By cutting his palm, he spreads his blood to envelop the clock, halting time at the school and catalyzing the "New Present." He murders Mitsuba Sousuke by exploiting his blood's toxicity, coldly dismissing Mitsuba's desire to become human. Later, during an escape attempt with Nene Yashiro from the "Place That Is Everywhere And Nowhere," he protects her by opening doors to minimize danger, though he ultimately cannot accompany her further. Trivia notes list his hobbies as fishing—where he catches mullets and "sometimes things that aren't fish, like girls"—and karaoke, especially idol songs. His favorite snack is black soybean senbei. His latest concern is Tsukasa's annoying behavior. He startles easily at lightning and lacks self-preservation instincts due to his immortality.