This is an honest opinion from someone who is a fan of the manga and the anime series: This drama was unnecessary.

~Story:
It would be one thing if this drama had taken a different approach with the story. Retell it in a different way, captivate the audience with exclusive content. However, what we got was an extremely glossed over version of a story that's supposed to be deep, intricate, beautiful, and heartbreaking.
This isn't a drama for the ones of us who are looking for a plot, this is a drama for those who want some lackluster fan service.
Given is a story told in different perspectives that interconnect in a harmonious way to form the bigger picture: we have Uenoyama's perspective, Mafuyu's perspective, Haruki and Akihiko's perspective, Hiiragi's perspective, and lastly Ugetsu's perspective. Unfortunately, this drama focused on Uenoyama's perspective and barely touched on Mafuyu's, the latter being the core of it all yet being undermined as if the writers weren't paying attention to the original plot. That being said, the entire plot contains huge holes that are very important for a clear understanding of what is truly going on. Everything is so shallow you can't even feel the despair or any type of emotion that should be there.

~Cast:
Nothing impressive. The actors provided little to no personality to the characters and left nothing remarkable to remember them at the end. Okay, you know what? I kinda take that back because Mafuyu's vocals are the best thing about this whole thing.
Sanari's vocals are to me the vocals anime Mafuyu should have had. No offense to the VA, but his vocals always made me feel as if he had breathing problems; on the other hand, Sanari's vocals felt like the wails of someone who's so deeply hurt they can't help but to cry in pain. It was B E A U T I F U L. When he started singing "Melody Lane," my heartstrings were being pulled by his voice in all the right ways.
Going back to the topic. None of them were bad actors, but it just felt as if they had never seen the anime or read the manga before. All of those moments that showcase the personality of each character were not there, and it is a shame because the characters have pretty great personalities and even better interactions with each other. All that is gone here.

The music is the one thing about this drama that truly deserves the spotlight. I already mentioned Mafuyu's vocals, but the musicians also deserve some credit because this soundtrack was IT.

I am going to be very honest with you, the reader: PLEASE DO NOT WATCH THIS DRAMA AS YOUR INTRODUCTION TO THE STORY. It is not even a shadow of how good the original source material is. This drama should be your LAST option because it's truly not at the level. DO NOT let this drama shape your opinion about the manga or the anime in any way.