Place it at the start of a sibling scene, just before the brother answers, then follow it with Anime Ahh for a flustered reaction or Onii-chan Onii-chan for a repeated call. Keep it as the opening beat so the next sound lands as the response.
このサウンドについて
This is a very short clip, lasting just over a second, of a high-pitched anime girl's voice calling out 'onii-chan' in a sweet, drawn-out way. It feels cute, playful and a little teasing, like a younger sister trying to get her big brother's attention. The bright, affectionate delivery makes it instantly recognisable as an anime-style call.