Akashic Records of Bastard Magic Instructor, Volume 9 (Akashic Records of Bastard Magic Instructor #37-40)

The Celestial Temple of Taum contains an ancient planetarium built by the mages of old, and Glenn's brought the whole class for a bit of archaeological exploration. Just when everything looks set to wrap up quietly, Sistine and Rumia accidentally discover the temple's secret: a mysterious portal leading to parts unknown. When Celica suddenly leaps through to mysteries beyond, there's no choice left but to follow her to the other side and stage a dangerous rescue!