Umm...her name is clearly listed in the credits under the picture, anastasia hoshin.
@Mizuho, The tags make no mention of Anastasia, nor does the commentary say anything about the character's identity. Could it be you got confused by pixiv adverts or common tags?
According to the character sheets in the light novels リューズ is Ryuzu. No idea what ビルマ is.
Birma, or possibly Bilma. Technically, it could be "Biruma", but when they actually want you to pronounce the "u" instead of being silent, they usually give it a smaller "u" or "yu" after it, like the "Ryuzu" has.
