The Fiend with Twenty Faces

This is a work that became a turning point in my life as a mystery novel fan. One day in the second grade, I went to the bookstore to buy the latest issue of my favorite manga. My father, who accompanied me, said, "Shall I buy you this too? It's interesting!" and bought me this novel. That was "The Fiend with Twenty Faces" with a silk hat on the cover. I didn't really intend to read it at first and read my target manga first... but the content was so shocking that I had nightmares that night as a second grader. My grandmother, who was sleeping with me, took both the novel and the manga away, saying, "It's because you read scary books!" (I later found out that the manga volume was so shocking that it became a legendary topic among fans for a long time). Feeling dejected, I went to school the next day... and what do you know! The same book was in the school library!!! I secretly read it without my grandmother knowing. I even brought a flashlight into my futon to read it. And then... I read it all at once and felt like my mind had been blown away by the "plot twist," a technique in mystery novels. I had never read such a long story before, so it also gave me confidence, thinking, "I can read this much!" What was the turning point work in your reading life?