Apparently, Disillusioned Adventurers Will Save the World, Vol. 4 (light novel)

After a fierce battle, Nick and the others succeeded in crushing the demon worshipper White Mask. The guild is extremely happy with their performance, and so the Survivors are entrusted with a job to guard a live concert by an idol. But when they discover counterfeit tickets-and a connection to the demon worshippers-they doubt that this is a normal escort job. Then Sun Knight captain Alice shares her suspicions about Nick's former party member Garos, shaking him to the core. Karan is there to support him, but her feelings for him seem to be changing...