Yang Tingting, also known as Yan, acts as assistant and companion to Mion within the experimental Program. She functions as a Regulator, maintaining order during battles. Her attire consists of a sleeveless red qipao. She possesses medium-length dark brown hair, styled with four distinct hair bun covers, and wears a watch on her right arm. Her eyes remain perpetually closed; this precaution prevents accidental activation of her ability.

Her demeanor typically reflects submissiveness and accommodation, consistent with her assistant role. She generally withholds personal sentiments unless circumstances necessitate their expression. As a Regulator, intervention within the Program demands explicit higher authorization. This restriction confines her primarily to observation, unless addressing significant protocol breaches.

Her designated ability, "Millennium Eye," propels time forward within her direct line of sight by one thousand years. Utilizing this power exacts a physical toll. Objects or individuals subjected to her gaze disintegrate or erode from existence through rapid aging. During the Fourth Program, she received authorization to deploy this ability against Leonhart after he violated battle regulations by eliminating a participant outside his designated team.

Her background and broader narrative development beyond her association with Mion and regulatory functions remain undocumented. Her actions remain strictly tied to her responsibilities within the Program's structure.