I May Be a Guild Receptionist, but I'll Solo Any Boss to Clock Out on Time, Vol. 5 (manga) — Mato Kousaka

The long-awaited centennial celebration! But an unsettling shadow creeps over Iffole unnoticed... Once a year, the entire city joins together in celebration, and the time for the hundredth celebration is almost here. Alina is overseeing the festivity preparations, but uninvited chaos arrives at the Iffole Counter when adventurers are enticed by false rumors of a secret quest through which they can obtain dia skills! Alina and her companions manage to corner Haitsu and his accomplices, but a momentary slip-up allows the culprits to escape. One member of Haitsu’s group gets left behind, and the man curses Lululee as a “murderer”?!