Someone who gathers the "receipts" (screen recordings, secret audio, or security footage) to expose the bully.
Instead of the mother believing the bully’s lies, Yuna provides undeniable proof. This usually happens in a dramatic "reveal" scene during a dinner party or a school event.
The goal? To "corrupt" the protagonist's mother—usually by lying about the protagonist's behavior, framing the victim for crimes they didn't commit, or driving a wedge of distrust between mother and child. In many original versions of these stories, the ending is tragic, leaving the protagonist isolated and the bully victorious. Who is Yuna?