The reasoning will be after dinner

Reiko (played by Keiko Kitagawa) is a wealthy lady of extremely high status, but most people are only familiar with her identity as an ordinary police officer. Kageyama (played by Sho Sakurai) is Reiko's loyal butler, always protecting her safety openly or secretly. On this day, Reiko encountered a case of a woman being killed in the house. Despite a thorough investigation, she still had no clue about the case, and her teammate Kazamatsu (played by Shiina Kihei) was just a playboy with an appearance, and had no talent except for making jokes. After the upset Reiko returned home, she couldn't help but sort out the information she got from Kageyama. Surprisingly, Kageyama said that he had deduced the entire process of the murder and who the murderer was, and even laughed at Reiko. After being unable to calm down, Reiko patiently listened to his narration and discovered that the silent Kageyama was really a reasoning genius! So, every day after dinner, Kageyama would accompany Reiko to start a journey of reasoning...