Invaders of the Rokujouma!?: Volume 8 — Takehaya

Back from his unexpected travels, Koutarou tries to settle in to his life as a normal high school student again. A school field trip to a ski resort sounds like just the right thing to do the trick. When they get there, however, Yurika notices that Maki is sneaking into the mountains to use magic. Worried that Darkness Rainbow is up to something, Yurika goes to investigate, but the investigation turns into a lot more than she bargained for when she comes across a demon.
The 9th book in the Invaders of the Rokujouma!? series!