A decent/good anime. Nothing special or groundbreaking and has quite a few deficiencies.

The animation is very good and the art is nice too. Very visually striking anime, some beautiful background art. Combined with the music there's a pretty decent atmosphere that helps to keep me engaged.

I personally found it to be an entertaining anime, and it really comes down to whether you like the two main characters. Because the story doesn't offer much else besides that. And I think that's fine. This is apparently made for a gacha game, so it's essentially just a marketing tool.
Because of this the story has no foundation to it, the symphonia, D2s, generic antagonists with vague or simplistic motivations. Its pretty clear that the creators didn't put too much effort into the logistics of the story. Stuff like the D2s and the villains are just plot devices to serve as a vehicle for the characters. I do think the story was at its strongest in the beginning where it didn't take itself as seriously, there was a lighter tone and a sense of adventure. When it introduced actual conflict and drama it fell apart because as previously mentioned there was no foundation to support it. Weak villains and weak side characters. The story would have benefitted from the initial premise of a travelling group of 3 and exploring the characters through their journey and monster killing

I found the two characters to be likeable and endearing with clear character arcs and serviceable character development. Takt closes off after his father's death with a very narrow minded obsession with music. He opens up due to cosette but still he obsesses over music and his perspective is still narrow. Eventually he comes to realise that music isn't just the lines on a sheet and the sounds an instrument makes. It's also the relationships he forms with others. This is apparent in two ways
He treasured music because it was important to him and made him happy Secondly, writing music requires passion and emotion. The bonds he has made with his friends, mentor etc become a part of his music through the passions and feelings they ignite within him. Before he was alone and depressed and so his view of music was superficial.

Destinys character is really just to provide Takt with an emotional anchor and to fill the shoes of Cosette. She's simple but shes endearing and gets the job done. The hook is essentially the story shows how Cosette got Takt to step back into the real world and there was a healthy relationship there but her turning into destiny means all of that is reset and now has to reform. Together theres some witty and engaging character interactions between them. These characters are restricted to familiar tropes but work well within that limited space to carry an otherwise empty story.