Don't bother with this one. Ys VIII was 5 or 6 times better.

Section 1: mechanics or design spoilers (not story spoilers)

The music didn't grab me.
Driving around in the ocean onto a buncha dinky islands to fight enemies that felt or looked the same got old quickly.
The story felt very basic or surface-level. It's just "let's fight the Greigr" for the whole game.
All the mana ride, mana string, etc. abilities were not fun and felt like someone had played too much tony hawk or spiderman lately. Get your platforming out of my RPG.
The boat starts out so slow it's painful to just sail out slowly slowly going anywhere.
Having only 2 characters in the party the whole time was a big minus. It lacked the dynamics and character depth that comes from interactions in a larger party.
Battle was silly because aside from the achievement for mastering single-person skills, there was no reason to not be in Duo mode the whole time. Duo mode is so strong, plus the game is constantly making you fight enemies that you 'must' use it to guard against attacks or to break through their barrier before you can damage them. Well OK the 1 reason to not always duo is to get achievements for mastering skills. That's it. Yes in the very last few hours I started to get some skills that might stack up against duo mode in some regards.
Despite being in control of Karja when initiating mutiple types of events involving Mana, tons of them switch to Adol and show him doing it. Ok, why did you give me two characters then? You couldn't render Karja holding her hand extended for 4 seconds using the normal game engine?

Warning: the next is a big story spoiler.

When a certain town was destroyed near the beginning of the game and the crew later learns the townspeople were turned into monsters, I thought oh since we fought our way out of town does that mean we killed some of the townspeople?! good lord. That is going to get awkward when we have to rescue some people and tell them we killed their family. But this concern is never addressed or even seems to cross the mind of a single character in the story. Despite the majority of characters having never heard of these monsters before, everyone magically knows that only a specific certain type (actually more than one type) of the monsters are former people. But.. but how do they know? They shouldn't. At this point I lost all concern about anything bad actually happening in the game, as it was clear everything just works out because plot armor.
In fact not one but at least two later islands prove humans can shift into other types as well, and yet still the crew doesn't act like we got lucky not becoming responsible for massacring a town. They just don't even consider the possibility -- that's what kills me.

Amazing combat system, but only two playable characters? Oh, I forgot --- it's because it's part of the main plot of the ♥♥♥♥♥♥♥♥ story.

In my opinion, buy this game if you are a fan of Ys.

This is probably a skill issue on my part, but I've played all of the Ys games and it has always been a game I can chill out and bash monsters in. In Ys X the combat controls utilize all of the shoulder and face buttons the controller and no matter how I remap them I can't consistently execute what I want to do and I just can't get into this game. I'm either inadvertently switching characters or holding the Duo attack/Block trigger instead of the Skill attack trigger, or dodging instead of mana string, etc. This is made worse by how faced paced the enemies can be, there's too much going on at once. I thought maybe this game would simplify things moving away from the larger parties of the last few games to focus on just two characters but the result is even messier experience.