Shojo ni Tensei Shita Shiriarukira wa, Mujihi ni Narr wo Oitsumeru

Nanaka, a woman in her 30s works as a jack-of-all-trades under the name of an exorcist. She meets a strange girl named Riru when she is asked to check on a distant relative. The requests she receives are rarely spiritual, and she often encounters so-called "scary" scenes. While listening to the client's story and trying to solve the mystery, she takes on Riru as her assistant, and with her unique talents, she leads them to solve one dark incident after another. She has a calm way of speaking and thinking that is hard to believe for a 10-year-old girl, and above all, she seems to know all about the thoughts of people who become criminals... Yes, inside her is a serial killer who was executed and killed. https://www.cmoa.jp/title/340980/