Do M Otoko Tantei ga Iku Katte ni Ittara Oshioki yo!

The story so far: Our pathetic, lazy hero and his childhood friend Satomi, as beautiful as she is brilliant. He lives his days in a hardboiled fantasy, playing at being a detective while barely managing to make ends meet. She's attending a top university and looking after him by acting as his reluctant partner. Never quite managing to make it past "just friends", the two get wrapped up in a startling incident, and suddenly things are turned upside down! Due to the actions of a mysterious man, Satomi is transformed into a super sadist whose thirst for punishment cannot be quenched!