This character is seen with a whistle.
A whistle or call is a simple aerophone, an instrument which produces sound from a stream of forced air. It may be mouth-operated, or powered by air pressure, steam, or other means. Whistles vary in size from a small slide whistle or nose flute type to a large multi-piped church organ.
When carried by characters in visual novels, whistles are typically the small variety, often worn around the neck.