Disturbing Schoolyard Tale

When a young woman was in high school, the entire female student body became especially fearful after discovering the dismembered body of a little girl in a trash bin on the school's playground. Since the restrooms were located outside the dormitories, female students always moved in pairs, with some brave boys volunteering to protect them. The restrooms were adjacent to the boys' dormitory, and male students often chivalrously guarded the area.

Later, the culprit was apprehended, and the reason behind the gruesome act was shocking. The killer had been timid since childhood, and someone had wrongly informed him that eating human flesh would make him braver. As a result, he murdered a young girl, cooked her flesh, and even used her fat for cooking. When his dormitory mates discovered that they had unknowingly consumed dishes prepared by the murderer, they were overcome with disgust.

But do you know how the culprit was caught? It turns out that the murderer had written the entire murder process in a diary, which was eventually found. Upon hearing the diary's contents, I was horrified because the killer was none other than the same young man who had actively protected the girls.