Having said that, if you watch the background carefully throughout the entirety of the series there are cherry blossoms and lots of them. This incites the feeling of Spring and thus New Beginnings. For the most part the series is quite light-hearted with more comical scenes than a normal mystery series should rightfully have however, there's a level of uncertainty that's suggested by Shoutarou's actions and hesitancy regarding Sakurako's behavior. This reflects our uncertainty and regret when overcoming our grief.
I believe the creator chose the mystery/murder theme because most people can relate to losing a loved one and it's not something that's easily overcome.
The mystery lover in me wishes that the serial case would have been introduced sooner and thus would have created a more mystery like setting but that would have ruined the creator's original purpose in.
The series doesn't pull its punches when it comes to revealing the depravity in human hearts nor its ultimately kind nature. I also loved that the series constantly brought up the "Two Truths", meaning that truth is somewhat relative to the knowledge we have and so is different for each person and each situation.
Having said all that if you watch this series expecting an awesome Sherlock Holmes type series you will be disappointed. There isn't enough factual substance for that, however if you come to the series looking for what it is actually giving then I doubt you will walk away feeling unsatisfied. In short, I think this series is a masterpiece for taking on a very depressing topic and turning it into a neutral subject that's actually fun to watch and experience.
