Zombie-Loan Vol 3

From the Yen Press edition

Though Chika and Shito manage to extract the girls from the clutches of the Butterfly Killer's fans, the case takes a shocking turn when an unexpected betrayal is revealed! With heavy hearts, the members of Z-Loan close the case, but they still can't shake the blues. So the Chancellor sponsors a group trip to the hot springs, which starts out all fun and games but ends with...a howl!?

Source: Yen Press