Nagisa Natsunagi Still Wants to Be a High School Girl, Vol. 1 (Light Novel): The Detective Is Already Dead, Ordinary Cases

All I wanted was to be a regular highschooler, and that wish is why I'm here right now. My name is Nagisa Natsunagi, and I'm just a high school girl, nothing more-not yet anyway. If there's one thing that's different about me, it's that, up until recently, I was too sick to come to school. Miraculously, I received a new heart, and the surgery was successful. Now I'm finally living the life I always wanted! But I can't help wondering about my donor...I hear there's a boy in town who can solve any case. Maybe he can help me?