Hotaru Haganezuka, a 37-year-old human swordsmith from the Swordsmith Village, serves the Demon Slayer Corps by forging Nichirin blades. He adorns a sunflower-patterned haori and a spotted head scarf, concealing his face behind a traditional Hyottoko mask. While traveling, a wide woven hat draped with floral wind chimes complements his attire. Unmasked, his sharp eyes, thick eyebrows, and long black hair reveal a face later marked by an X-shaped scar and a blinded left eye after surviving an assault by Upper Rank Five demon Gyokko. Intense mountain training prior to this clash reshaped his physique into a more muscular frame. Born into the Haganezuka Clan, his fiery temperament strained his parents’ mental health, prompting village chief Tecchin Tecchikawahara to raise him. The chief named him "Hotaru" (firefly), a moniker he resents for its delicate connotations. A master of his craft, Hotaru pours obsessive dedication into forging and polishing Nichirin swords, delivering impassioned lectures about their intricacies. Damage to his creations—especially Tanjiro Kamado’s blade—triggers explosive fury, soothed only by mitarashi dango. His social awkwardness and single-minded focus alienated peers, costing him clients, yet he privately values Tanjiro’s unwavering trust. Initially encountering Tanjiro to repair his unique black Nichirin sword, Hotaru evolves into a pivotal ally, supplying weapons for the slayer’s demon-hunting missions. Though untrained in combat, he wields tantōjutsu with skill and, after rigorous mountain training, gains the strength to endure demon attacks. His surname, meaning "steel," reflects his profession, while the wind chimes on his hat echo a childhood remedy for his tantrums—a habit retained into adulthood. A peculiar weakness exists: tickling his sides disrupts his focus, rendering him limp momentarily. Beneath his volatile exterior lies an unyielding commitment to his craft and the Corps, etching his role as both artisan and reluctant warrior.