The mist is likely a border set up by Yukari. They mention thick fog which I presume is what lets Flandre roam around. She was able to fight in a darkened forest in 17.5 as well albeit being in one of the non-canon routes.If I remember correctly, ZUN once said a long time ago that if Flandre got loose outside, the damage would be irreparable. So Wither she's possessed or, as @parodyres said, Okina's once again using someone else to do her dirty work.
Also, can someone remind me as to whether vampires in Touhou are weakened to sunlight? Because Flan look well and truly dandy for a youkai that allegedly turns to ash in broad daylight.
No actual source, but in this manga Flandre mentioned that they dislike sunlight (not afraid of it), so in my opinion, sunlight for Touhou's vampire is equal to desert's heat for normal humans.Also, can someone remind me as to whether vampires in Touhou are weakened to sunlight? Because Flan look well and truly dandy for a youkai that allegedly turns to ash in broad daylight.
Well in Silent Sinner in Blue, Remilia's wing caught a little bit on fire for being in the sunlight for too long, so there is some direct physical harm from long exposure.No actual source, but in this manga Flandre mentioned that they dislike sunlight (not afraid of it), so in my opinion, sunlight for Touhou's vampire is equal to desert's heat for normal humans.