Ruby-chan refers to Ruby Kurosawa, the shy idol character from Love Live Sunshine, whose name fans call out in affectionate edits and fan videos. This short hai response format spread as a reusable soundboard clip because the exchange is complete in under two seconds and needs no setup. Creators reuse it across anime edits, streams and chat soundboards as an instant signal of enthusiasm and cuteness. Its popularity comes from that simplicity, along with similar cute anime voice clips like the tuturu sound that fans drop for a recognisable reaction.