Celica Ayatsuki Mercury (セリカ＝アヤツキ＝マーキュリー Serika Ayatsuki Mākyurī), also known as Sister (シスター Shisutā), is the younger sister of Konoe Ayatsuki Mercury, and aunt of Kokonoe Mercury. She is one of the main protagonists in the Phase Shift novels and appeared as an NPC character in BlazBlue: Chronophantasma before becoming a playable character starting from BlazBlue: Chronophantasma Extend onward.