Yuina Oosawa

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.

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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)