This clip circulates online as an anime reaction sound built around the Japanese term “oniichan,” a common way to address an older brother in anime and manga. Short edits on soundboards, meme compilations and reaction videos helped it spread because the delivery is instantly readable even without context. It stays popular for the same reason as Onii-chan, onii-chan and other exaggerated anime voice snippets: creators can drop it into a scene to signal clingy disappointment, embarrassment or playful melodrama in a fraction of a second.