In Lost Judgement: The Kaito Files, your character can find and unlock three important skill books. While these books do not directly help the player gain skills, they are extremely important because you cannot purchase a skill until you have unlocked that skill book.
Lost Judgement Kaito Files – How to use disguises in free roam
Likewise, the Disguise Fundamentals is the third and final skill book that you need to find. However, obtaining this item is difficult as the process is quite complicated. If you can’t find the location of this item, here is a complete walkthrough that will help you obtain this skill book.
Once you progress through the main story and are nearing the end of this expansion, Kaito will attend a social gathering in Kamurocho as part of his investigation. Once you return, you will be given a warning and the game will ask you to complete all of your previous tasks before you can begin the next mission.
After you get this warning, you need to go to Ebisu Pawn. You can find this shop once you enter the narrow alley between Nakamichi Street and Pink Street. In order to get the skill, you need to buy the book first. Therefore, you need to buy the Disguise Fundamentals book from the NPC in this shop for 50,000 yen.