Niryu lives within the deeper spaces of the ocean, close to the trenches that spread across the sea floor. She's very shy, and very to the point when she speaks. She grows especially nervous when around too many people at once. She prefers the quiet company of fish, as they require little in the way of communication.

In her free time, she sometimes likes to wander along the ocean floor in search of interesting objects that have sunk to the bottom from careless humans or other mermaids.