magus in mystic geometries
神魔討綺伝 (Shinma Touki Den - lit. "The Legend of God Demonic")
A Touhou fangame by D.N.A.Softwares. The sole playable character is Patchouli Knowledge while the only known boss is Shinki. The plot involves inhabitants from Makai once again lurking in Gensokyo, so Patchouli goes out to take care of them. ZUN has contributed to the game, giving Shinki a unique theme.
Note that images that mostly only contain Patchouli and Shinki are likely references to this game.