Kayano

She is first introduced in 'Boukan no Rebellion' as a masked woman, working for SERN, who confronts Suzuha in 2036 after her failed attempt to snipe the commander of the "Rounder Executive Squad" (after failing to assassinate Makise Kurisu beforehand) She is the one who murdered Suzuha's mother in 2036, shortly before she went back in time to 2010.