The author has taken ideas from both novels and BBC series. Moriarty's character is written well although in books he was quite different. If you like Sherlock Holmes, you will like this series. There's also intense gore, which is not mentioned above in the description.
When they found the body, the victim was laying on his back. If he died trying to unlock the door, why did he turn back and lay down instead of falling on his front. and why did the culprit count on victim's mistake for locking himself. what if he didn't make the mistake?
i thought it would go like this: The pendant and toru were the key to her sadness. she would ask toru to find it and he would find it, then she would fall in love with him but he would reject her because he likes sasamori, that's why she will become sad.