The plot is beautiful. I personally love these kind of stories. We were given some graphic scenes which is appreciated.
For a movie that its about a serial killer, we don't see him killing in many scenes. Actually we just see Morozumi hurting Yamashiro once, but I think this might be intended hence the ending.
The actors did well, Fukase Satori's role was nailed, he really looked crazy and its good that way. I was expecting a "fuckboy" style of murderer because that's what's hot right now and it was a nice reward it wasn't that way.
Midway through the movie I got a little bit lost regarding time lapses. The movie appears to go slower than it really is, which is confusing. Although with the crime scenes you can notice time has passed since the bodies are rotten, its strange and it feels like they were running out of time when they actually had plenty.
The details put into the backgrounds and the scenery shows this movie was made with love and care. It was pleasant to see so many things, so stimulating and encouraging to rewatch and not lose any detail! It does makes you want to read the manga.
Characters could've been developed/described better but overall a nice movie, enjoyable and would rewatch of course.
It leaves some holes and a semi-open ending, I'm afraid a sequel could screw up what we have, I didn't see any news about it, but I hope its good in case its coming.

TL;DR
Good plot, excellent scenery, nice actors. Weird execution regarding time, characters could've been better.