Koseki Bijou, nicknamed Biboo by fans, is a virtual YouTuber with Hololive English's Advent generation, which debuted in 2023. Known for her playful gremlin energy and expressive reactions, she often drops exaggerated disgusted lines like 'ew, stinky' during livestreams and collabs. Fans clipped the moment and spread it through VTuber highlight channels, TikTok edits and meme compilations, where her cutesy delivery turned a simple insult into a reusable reaction. It endures because Hololive clips travel fast and the line fits any gross-out or roasting context.