I'm a librarian who loves anime, manga, and reading a wide variety of genres.
This is going to be a quick read, from the looks of it. As Death Note fanfic, it's interesting enough, with lots of asides and cameos meant for fans of the original series. As a mystery, I'm currently unimpressed.
The setup is okay. Three locked room mysteries involving an obsessive killer who completely cleans up all possible fingerprints in the victims' homes, going so far as to unscrew light bulbs and wipe the sockets. The killer's methods differ from one murder to the next - the only thing all three have in common (aside from the victims' odd names) is that obsessive cleanup and the Wara Ningyo dolls nailed on the outside walls of the homes, always one less at each murder. It seems that the killer also left other clues the police didn't catch, that L and Misora, his temporary assistant, have just started to find. Unless L has already found them all and is just waiting for Misora to catch up.
The problem is that, so far, more time has been spent on describing L acting weird and mysterious than on the murders themselves. We just know that the first clue (a crossword puzzle) was very difficult, so difficult that the police couldn't figure it out, but of course L could. Although the author has the opportunity to show us this crossword puzzle, he doesn't - it's just mentioned in vague terms. I figured out the basics of the next clue so fast that it made me doubt Misora's intelligence that she didn't at least get that far.
And now we have L fishing for compliments.
Okay, so Misora doesn't actually know she's in the same room as L right now. She thinks she's communicating with him via cellphone and that the guy in the room with her is someone completely different. (Why L enlisted her help if he was planning to investigate on his own baffles me.) She gets suspicious, calls L up, and describes the situation and this "stranger" to him. His response:
"'Was he cool?'
L's question came completely out of left field, and he was forced to ask it a second time before Misora answered, still unable to work out what he was driving at.
'No, absolutely not,' she said, honestly. 'Creepy and pathetic, and so suspicious that if I weren't on leave, I'd move to arrest him the moment I laid eyes on him. If we divided everyone in the world into those that would be better off dead and those that wouldn't, there's no doubt in my mind that he'd be the former. Such a complete freak that it amazes me he hasn't killed himself.'
I have a feeling that Nisioisin intended this to be humorous (L fishing for compliments and getting the exact opposite), but it was so over-the-top harsh that it actually made me gasp. Yes, he's creepy, suspicious, and weird, but saying he'd be better off dead and that it's a wonder he hasn't committed suicide is just plain horrible.