Apparently, Disillusioned Adventurers Will Save the World, Vol. 1 (manga)

Life isn't going well for veteran adventurer Nick. Despite his loyalty to his party, he was betrayed by a teammate who accused him of embezzlement, then kicked out by his mentor. On top of that, his girlfriend dumped him too! Tired, heartbroken, and looking for a drink, Nick chances upon a few kindred spirits who are as jaded as he is. Can these disillusioned heroes put their faith in each other long enough to save the world together…?

Volume 1 of the Apparently, Disillusioned Adventurers Will Save the World manga series by Luke Hutton.