KNY is the common abbreviation for Kimetsu no Yaiba, the Japanese title of Demon Slayer, the manga by Koyoharu Gotouge that was adapted into an anime by Ufotable in 2019. The series centres on Demon Slayers who fight with Nichirin swords using distinct Breathing techniques, so sharp blade sounds are a core part of its action scenes. Short slice clips taken from or inspired by those fights spread widely in anime edits and soundboards, where fans reuse them for other sword characters and fast-paced battle sequences.