She was introduce in ep.9, as a mysterious returning student who is with the Katahira Faction, she took over the leadership of Public Safety Commission from Mouri as a precondition that Kana be admitted in a hospital which is run by the said faction.

Spoiler

She is the one who ran over Kana while investigating certain anomalies involving the General Affairs dept in which she is part of.

(Source: Otaku-streamers forum)