This show was handled rather well, especially in hindsight. There were some flubs which made the writing come across poorly if not actually so, but overall it worked with what it was doing.
There will be partial spoilers in my quick summaries for each rating. I'll try to be fairly vague with that stuff tho
I feel the story it was aiming for was implemented well through-out and, especially in hindsight, anything that felt off made a lot more sense. But it takes until a major event for this to begin making sense unless you already know about it or are just that good at picking up the subtle hints.
Tho there were some things that didn't work quite so well despite that, such as if something repeats itself then it should never have been so similar as if it were the original.
And in regards to recanting memories after a big event, without them having to show everything, it was off-putting. Some serious liberties were taken to keep it interesting, concise, and simple. But the tone was off from the rest of the story and so I felt it wasn't done well and it still bugs me. I'm also not a fan of memories in which stuff not actually experienced was shown so, again, it wasn't done well and is a big reason I'd never give this a 10.
There were moments where there were some animation issues never corrected after broadcast, such as chunky hands for a bit and face markings disappearing for one scene where frames weren't reused. Overall tho there's nothing so distracting it can't be overlooked.
Design-wise, I yawned far too frequently for. Some made sense given their character and their place in the story, but most I just didn't care for. It gave a nostalgic feel tho so it wasn't unbearable while watching. Just nothing I'd have watched the series for, which is probably not a good thing in regard to marketing.
Honestly, for a story in which songs are so vital to the plot, they were seriously lackluster. While they had a style of their own instead of just throwing in some modern or retro sounds, there was so little that felt it was magical or even memorable.
There was nothing special or awful about the quality, sfx, or bkg music either. Other than Tamura singing tons.
The sisters bored me from the get-go. Would've enjoyed it much more if they didn't just toss them in and kept them, as they gave the "one-off" vibe far too much even to the end. This forcing of a ~symphony~ honestly lowered the quality of the cast. Without them, it probably would be more along the lines of an 8.
The rest of the cast was fine tho. A good chunk of them actually grew through-out and very few remained static. There were many one-off characters but, given the adventure/traveling type plot, it was reasonable and didn't hinder anything.
I could ignore the sisters being worthless to the story, and the annoyance of a kid genius, and even the random writing flubs.
The second I got the reasoning for some inconsistencies, I was constantly thinking back of them while finishing the show; the way memories (not flashbacks) were recounted allowed time to actually remember what I was binging.
The fact that the songs were so unremarkable - especially the duet - lowered this rating from a 9.