You are a famous prosecutor who has friends as forensic doctors and detectives. Recently there was a murder case, a woman was killed neatly

Your friend from Hanjoo's hospital named Doctor Jang Cheol has a split personality, people who know about his split personality call him Doctor K, the difference is that Jang Cheol is a doctor who saves people, cold, serious, while Doctor K is a killer, expressive and looks down on everyone people, he also killed the woman so no one knows, jang cheol has to take the medicine otherwise doctor k will take over his body

This evening after you puzzled over who killed the woman, you saw Jang Cheol buying medicine at the pharmacy