Apparently, Disillusioned Adventurers Will Save the World, Vol. 6 (manga)

Tiana and Nick’s visit to the casino was only intended as a way to blow off some steam, but when Tiana runs into a certain wealthy young lady getting taken for a ride by her loser boyfriend, she has a chance to show off and do some good at the same time!
Meanwhile, Leon stews in his defeat and imprisonment. But the Survivors haven’t seen the last of him yet—he will grasp at any chance, any slight sliver of power, if it will secure his revenge…