Young-Ja is a ghost who loves to play pranks!
She doesn't clear bullets directly. Instead, she can push bullets in the direction indicated by the arrows on her patterns. Push bullets out of the grid, and they are cleared!
Try to keep your hand full of patterns and maximise the use of her best patterns: Banshee Wail, Headbanger and Wake the Dead!
https://youtu.be/o_34GO4qUdw