Party at Walter Park After safely passing their exams, Iruma and his friends start their end of terminus break from classes with a trip to Walter Park! Little do they know, however, the famous netherworld amusement park is actually built on top of a prison fortress whose inmates are hatching a sinister plan of monstrous proportions…!

Volume 9 of the Welcome to Demon School! Iruma-kun manga series by Osamu Nishi.