Koga Oogami attends Yumenosaki Private Academy, progressing from Class 2-B to Class 3-B. He measures 174cm tall as a second-year, growing to 175cm in his third year, and weighs 58kg. Spiky grey hair falls just below his ears, featuring bangs that cross in the middle, paired with light golden eyes. He customizes the school uniform, wearing the white shirt untucked with the collar unbuttoned and adding a non-standard black tie displaying a white sideways cross. A long-sleeved purple shirt with holes is often visible underneath. Accessories include a silver spiked earring on his left ear, two helix piercings on his right ear, a silver ring on his left middle finger, and dark red boots. For UNDEAD performances, his attire includes a fur-lined half-sleeve jacket over a dark grey v-neck shirt, black pants, high boots, a studded choker, a fingerless glove on his left hand, and a black peaked cap decorated with silver studs. Wild and hearty, Koga exhibits strong self-confidence, frequently calling himself a "proud lone wolf." He possesses a quick temper and acts impulsively, openly snapping at others regardless of status, often using threats like "I'll bite you!" or growling at disliked individuals. Despite this abrasive exterior, he holds a sensible and caring side, deeply valuing close relationships like those with his UNDEAD unit mates and the Producer. His keen sense of smell makes him dislike strong odors, and he has a noted aversion to cute things and sweets. His name reflects his traits: the characters mean "bright, brilliant" (晃) and "fang" (牙), while his surname Ōgami (大神) translates to "great deity" but puns on ōkami (狼), meaning "wolf," alluding to his wild demeanor, physical prowess, and acute senses. Koga grew up in an average household with doting parents. His family adopted a corgi named Leon during his childhood, whom he loves unconditionally; Leon's friendship with Subaru Akehoshi's dog, Daikichi, facilitated Koga's bond with Subaru. Due to the long commute from his family home, Koga began living alone in an apartment during his second year. To reduce living expenses, he took up vegetable gardening in the academy's plot, growing tomatoes and other produce. He once cultivated garlic intending to use it against Rei Sakuma—who dislikes strong smells—but ultimately gave it away due to the odor. Koga is a central member of the unit UNDEAD under Rhythm Link, a name he chose himself. He aims to perform "the best rock music ever," striving to transcend traditional idol boundaries with high-energy, passionate performances marked by his zealous singing voice and dynamic stage presence. He handles most of UNDEAD's music composition and is a skilled electric guitarist, having sworn to protect his instrument "with his life." Historically, during the "War Era," he was part of DEADMANS alongside Rei Sakuma and Keito Hasumi. While Koga often displays hostility toward Rei—frequently calling him "vampire bastard"—he inwardly admires and respects him, acknowledging Rei's role in shaping UNDEAD. Rei finds Koga "adorable" and notes his significance to the unit's identity. Koga shares a close friendship with Adonis Otogari but harbors irritation toward Kaoru Hakaze, often hesitating before adding "-senpai" to Kaoru's name. His character development shows a shift from rivalry to nuanced loyalty, evident in his protectiveness during events like Halloween, where he sulked after Adonis dismissed his enthusiasm. Outside music, Koga excels at card games, once known in elementary school as “Kou-chan, the Wolf Tamer That Howls On A Full Moon.” He suffers from pollen allergies and avoids medical injections when possible. His autograph stylizes his surname's "O" as a wolf baring its fangs, reinforcing his self-proclaimed wolf persona. Dogs are naturally attracted to him, aligning with his affinity for Leon. His character evolves from a flashy, rebellious figure to one balancing his "wild wolf" identity with moments of earnest vulnerability, particularly in his dedication to UNDEAD's ideals and his discreet acts of care for others.