Character A: Reimu Hakurei
Character B: Remilia Scarlet
Character C: Yuyuko Saigyouji
First, there's Reimu Hakurei (博麗 霊夢), the main character of the Touhou Project series (along with Marisa Kirisame) and the shrine maiden of the Hakurei Shrine. Her first appearance is Touhou Reiiden (Wondrous Tale)~ The Highly Responsive to Prayers (東方靈異伝 ~ The Highly Responsive to Prayers) and right now, her current design is from The Embodiment of Scarlet Devil.
Next, there's Scarlet Devil herself a.k.a. Remilia Scarlet (レミリア・ス