Hazure Skill: The Guild Member with a Worthless Skill Is Actually a Legendary Assassin, Vol. 1 (Manga), Paperback

After defeating the demon lord, assassin Roland seems destined for eternal greatness, yet he wants nothing of the sort! Determined to avoid fame and fortune in pursuit of a normal life, he applies for a job at the local Adventurers Guild, where all manner of intrepid warriors come to turn in their quests. But Roland has no idea what "normal" really is, and he's anything but your average employee! Will this world-class assassin be able to adjust to the monotony of everyday life at the guild?