Hazure Skill: The Guild Member with a Worthless Skill Is Actually a Legendary Assassin, Vol. 3 (manga)

The world's deadliest assassin has settled in nicely at the guild, and he's quickly become their best employee. What's more, all the girls at work can't get enough of him, even if he's too oblivious to notice! But he's got bigger things to worry about, as his partner Rila, the former Demon Lord, has been kidnapped, and he'll have to go up against one of her most trusted allies to get her back. But was Rila's disappearance truly a kidnapping...or was it an escape?