Instrument:
Spector EURO 4 LX RAS LAYER -Twilight Amber-

A second-year high school student. She goes by the moniker LAYER and is the vocalist and bassist for the band RAISE A SUILEN. She is Tae's childhood friend. Due to Rei's mature attitude, she has a tendency keep a certain feeling of distance with others.
She has liked singing since she was young, and now she is a professional singer who can sing any song. In addition to temporary part-time singing jobs, she used to play bass in a back up band for famous artists. Rei had also attended the same music school as Tae and Arisa.
(Source: BanG Dream Wikia, edited)