Hotaru Haganezuka is a swordsmith affiliated with the Demon Killing Corps.
Haganezuka first appears in the manga when he delivers Tanjirou's katana to him at Urokodaki's home. He appears wearing a sunflower patterned robe and a large woven hat with floral wind chimes hanging from it. His head is wrapped in a spotted cloth and his face is concealed by a Hyottoko mask (wooden festival mask) similar to Urokodaki.
(Source: Kimetsu no Yaiba Fandom)