Oyasumi is a common Japanese greeting used before sleeping, roughly meaning good night, and short clips of characters and streamers saying it have become popular as soundboard reactions. The Zeta version circulated in anime and VTuber fan spaces where fans collect favorite voice lines as short, shareable audios. Its appeal is the contrast between its tiny length and its cozy, intimate mood, so it keeps being reused for stream endings, Discord good nights, and edits that want a soft punchline instead of a loud meme.