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

In recognition of his skills and accomplishments, the guild master promotes Roland, former legendary assassin, to the position of tactical advisor. As Roland directs a large-scale quest at the behest of his superiors, however, he finds his old companion Lina in a strange cavern-and a malicious force using her magical powers for evil!