Also known as: 魔天使, 封魔録四面中ボス
Matenshi (魔天使) is a humanoid of some kind that bares the resemblance of an angel and is the stage 4 midboss of Story of Eastern Wonderland twice. There is no dialogue or any official information about her.
Her sprite shows that she has Purple Hair at medium length and wears a long, Blue Dress. She has an Apron with a cross on it, and also has White Wings. Since she's got angel-like wings and a holy attire, she's possibly an Angel. However, Reimaden might be in Makai, which can therefore indicate that she's a demon with the fact that Gengetsu also has angel wings. Her design somewhat resembles Sariel's.
https://en.touhouwiki.net/wiki/Minor_Characters/PC-98#matenshi