Hazure Skill: The Guild Member With a Worthless Skill Is Actually a Legendary Assassin, Vol. 6 (Light Novel)

INVESTIGATING MYSTERIOUS TECHNOLOGIES! Roland's victory over Amy came at a high price, and Rila's collar was destroyed in the process. Hoping to repair the powerful item, the former assassin searches for its creator, which leads him to an old friend. Meanwhile, tragedy strikes in Rubens when its king is found dead. Only one of the greatest assassins in the world could have done this. It almost seems like Roland himself was responsible...