Pretty much a continuation of the Ys 8 design philosophy, music is great, graphics are nice and story is interesting, even if the ending feels rushed, because the game plays coy during dozens of hours and doesn't show its hand until the very end, at least is better than the ending of Ys 8 (still sour about it)
That said, by the end I was bored out of my mind, despite the combat being almost identical to Ys 8, the increased volume of enemies encouraged me to spam skills, of which not many felt satisfactory to use. On top of that, unlike Ys 8, the difference between a lvl 1 and lvl 3 skill is barely perceptible (massive let down), not to mention that getting attacked by 6 enemies at the same time also forces you to overrely on the dodge mechanic that doesn't work very well because enemies track you after commiting to an attack and hitboxes are all over the place. So the best bet is to use the strongest chaarcter, equip a lifestealing accesory and just go berserk (Yufa was my main character the whole game)
Another huge let down was the lack of a romantic interest for Adol, I mean, the 16 year old girl has a crush on him but I had to use all the dialogue options to shoot her down because Adol is 24 and that would be, to put it mildly, highly problematic (Yufa was right there, wtf, Japan). I loved to tease Laxia in Ys 8, and, alas, it was not possible this time around.
I think it was a mistake to make it the central location of the game. Of the entire city you can only enter a handfulof buildings, sure, you shouldn't be supposed to enter every building, but I have no doubts someone was being cheap when I saw the pub owner standing in the street selling food instead of, you know, being inside the pub. Yet another point where Ys 8 was better, that deserted island was a great excuse to get rid of pointless npcs and buildings, of which there are many in Ys 9.
Overall, I think Ys 8 did it all better, except for the ending, and the music. Still worth a playthrough.