This is one of those times when I believe the summary doesn't really done its anime storyline's justice.
If you like stories about developing friendship, beautiful soundtracks, and/or touching slice-of-lifes, this is for you.
Story - 8/10 (very good)
Ah, another story about reliving an unpopular school club. It's one of my most liked tropes, so I might just be a little biased here.
A shy, timid guy wants to keep his club going for the sake of his graduated senpai. The premise is quite simple, you see. But the way the director is telling it to us, the audience, managed to bring along the stories of its characters' both struggles and simple happiness moments to be wrapped up into something simply beautiful. The storytelling style is one of my favorite parts of this. The way they revealed the flashbacks little by little in each episodes from multiple POVs makes it easier to sympathize with the characters.
Characters - 8/10 (very good)
The characters development is the big selling point in this, and the thing that keep the plot going. My favorite character in this is Kudo, if I have to say. I love how (realistically) complex his characterization is. He is a pessimist that has partly given up on himself but still yet striving to do the best because he's longing for a good future. Despite how the MAl summary sounds pretty Takezo-centered, the story itself is actually more Kudo and Hozuki-centered.
The biggest downside that hold me back from giving its characterization point 10 is how Hozuki character had written. The genius but having too strict parent is already a quite often used troupe. Without bringing anything new to her character except having dual upfront personalities (which actually not that different) her character just seems too cliche.
Overall though, I love the character developments that most of the main characters had shown.
Art - 6/10 (okay)
No lies here, the art itself is nothing than just okay. In my opinion, at least. But I think many people would agree with me, even though everyone's personal scoring might differs. Nothing special about the art. Almost all of the characters design would give you some kind of Deja Vu cause its been used similary in any other anime. The color palette is even rather dull for this kind of story, in my opinion.
Sound - 10/10 (amazing)
I'd give nothing less for the sound. The Koto instruments sounds truly beautiful. The voice actors done their job greatly, especially for Takezo's voice. They insert the right soundtracks in the right times and it really helps bringing up the overall mood. The opening and ending themes might slightly less amazing, but I'm willing to overlook that for the sake of doing the instrumentals justice because Koto really does sound amazing in the right hands. For that, I'm really glad they had made this anime.
Overall - 8/10
This is something I'd definitely continue to watch and would recommend to anyone looking for a good SOL anime.