Hotaru Haganezuka

left|thumb|Hotaru's hot-blooded and fiery personality. Hotaru is a rather hot-blooded individual. He seems to show very little care, if any, about anything besides the swords he creates. His passion for swords is so strong that he would be able to speak about them for long periods of time, a trait unique even among other swordsmiths. The same passion that gives him the enthusiasm and extreme dedication in creating swords is also the reason why he is easily enraged (usually in a comical fashion) towards swordsmen who misuses his creations, especially Tanjiro Kamado, no matter the circumstance. When angry, he usually calms himself down by eating mitarashi dango. Bystanders can subdue him by either pinning him down or tickling his sides, as demonstrated by Kozo Kanamori, after which he will fall limp. thumb|Hotaru being tickled by Kozo to calm him. As Hotaru is socially inept in dealing with people, he is still unmarried. His intense and asocial behavior also causes other swordsmen to hate him and he lost a lot of clients because of this. Although he won't be honest about it, he is actually happy that Tanjiro still trusts him in making his swords. His concentration on sword-making is so immense that it prevents him from paying any attention to his surroundings when forging a blade, even when a demon is attacking him and inflicting severe injuries on him. When the process of forging or refining is interrupted by taking the sword away, he feels the need to restart the whole process from scratch again. As a perfectionist, any small scratch on a blade that is irremovable hurts him immensely. Despite his notorious asocial and volatile personality, he shows a more surprisingly pacified and rational side when a woman that Kozo, Tecchin, and Kotetsu attempted to matchmake with Hotaru degrades swords as antiquated and barbaric. Hotaru points out the perseverance that Demon Slayers display and the daily risks they face and proclaims that he is proud to forge swords for them, and frankly turns her down. This shows that despite his unruly and borderline insubordinate personality, Hotaru does have a deep respect for the Demon Slayers.

Hotaru wears a black yukata with sunflower-patterned haori over it and has his head wrapped in a spotted head scarf. Like the rest of the swordsmiths, his face is concealed by a Hyottoko mask (wooden festival mask) to conceal his identity. When traveling he wears a large, woven hat with hanging floral wind chimes on top of the head scarf. When enraged at Tanjiro losing his sword for the second time, Hotaru takes off his haori and opens up his yukata to show his chest a bit more, also turning his head scarf into a headband, using it to display two knives on his head and reveal his long black-hair. During the Swordsmith Village Arc, he is seen with a more muscular build compared to his initial appearance after he had been training in the mountains. In addition, a lock of his hair is exposed from his scarf. Unmasked, Hotaru's long, black hair is fully freed and his revealed to have sharp eyes coupled with distinctly-shaped thick eyebrows. However upon being attacked by Upper Rank Five, Gyokko, Hotaru now possesses several deep scars and cuts from the demon all over his body, including an X-shaped one on his face, and has now lost the use of his left eye.

thumb|Hotaru continues to polish his blade whilst heavily wounded by Gyokko. Overall Abilities: Being a swordsmith, Hotaru initially did not appear to have any kind of superhuman abilities similar to Demon Slayers. However, after Tanjiro broke his Nichirin Sword multiple times against members of the Lower and Upper Ranks, he underwent a special solitary training regimen in the mountains so he could forge a stronger blade for Tanjiro. As such, his physique was greatly enhanced with prominent musculature, enough to even overpower Tanjiro when he pulled away a blade from his hands. Additionally, Hotaru survived an onslaught of attacks by Gyokko, the Upper Rank Five, even confusing the demon with his unrelenting commitment to polishing his blade and ignoring his many injuries. left|thumb|Hotaru ignores being slashed by Gyokko. Enhanced Stamina: Mostly used as comic relief, Haganezuka has absurd amounts of stamina, evidenced by relentlessly pursuing Tanjiro for hours from evening to morning, and even made another attempt the following day. In both instances Tanjiro was left exhausted. Hotaru also survived being attacked by Gyokko's sharp tendrils of water. Enhanced Strength: After training in the mountains, his increased strength apparently exceeded that of even Tanjiro, able to pull the ancient sword from his grasp and even shoving him to the ground. Master Swordsmith: Hotaru is a master swordsmith, able to forge Nichirin Swords and repair it multiple times each time it broke in battles against demons. After Tanjiro chipped his sword in his battle against Upper Rank Six, Hotaru trained himself more to make a stronger sword. Hotaru demonstrated his professionalism and expertise when he polished and sharpened the 300-year-old blade left in Yoriichi Type Zero while completely ignoring the wounds he received from Gyokko. The polishing techniques he used has been passed down the Haganezuka line for many generations. His method is so severe that other swordsmiths have died from them. Aside from Nichirin swords, Hotaru also crafted kitchen knives which are dangerously sharp which he use as weapons.