Tokyo: Starting from Joining a Detective Agency

Travel to Tokyo in the 1990s and become a person who "shouldn't exist". Fortunately, there is a golden finger that "you will know who has the secrets of who you are targeting". Let's work part-time as a detective first, just in time to save the president of the detective agency who wanted to hang himself because "the child is not his" and "his wife ran away with someone else". The detective industry in reality is completely different from "Conan-style solving crimes": catching rapes is the main job, and miscellaneous tasks are daily life. The first task: investigate a beautiful wife and get evidence of her cheating. The client was not the wife's husband who was on a business trip, but a colleague from the high school where the wife worked. Shuhei received accurate information: the wife had not cheated on her, did not have a husband, and was single. But the client has to get evidence of her cheating, otherwise he won't pay... By the way, how should I solve my "black account" problem?