The Detective is Already Dead

I, Kimihiko Kimizuka, was an ordinary high school student. Sure, I had a penchant for getting dragged into all sorts of trouble, but was otherwise ordinary-until I met her. The detective, Siesta. Her angelically beautiful face and cool disposition in the face of plane hijackers swept me off my feet…and the next thing I knew, I’d spent the next three years off on a whirlwind adventure acting as her assistant. After all, I was the Watson to her Sherlock. But then…she died. It didn’t end there, though. No, our story only really began a year later when I met a bratty, snotty high school girl who seemed oddly familiar… (Source: Yen Press)

A slice-of-life romantic comedy between a certain famous detective and her assistant from "The Detective is Already Dead."

All I wanted was to be a regular high schooler, 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? (Source: Yen Press)

A romantic comedy depicting school life with Siesta.

"Tantei wa Mou, Shinde Iru." but this is a romantic comedy manga.