I think Ys is one of the best action RPG series out there. I played a bit when I was younger, but I truly discovered it in the past years. All games in the series are worth a playthrough and they all have common qualities, although each game feels unique (even if you play the same character -Adol Christin- in most of them!)

Common strengths of the series are: the consistently excellent music; the quick and exciting gameplay, coupled with satisfying level progression; the relatively small scope of each game, especially before the modern party-based entries; the excellent writing and worldbuilding, including an epic story, strong plot twists and a good amount of cheeky humour.

Here's my personal and very subjective list of what to play in the Ys series. Just know that they are all standalone games, and are not published in chronological order of the story.

**MUST-PLAY TIER
- YS ORIGIN: If you're playing only one, I think it should be this one: as the last game made before modern party-based titles, Origin sits perfectly between Ys eras. The game itself is set centuries before the rest of the series, offering a good understanding of its foundational lore. It also has 3 interwoven stories that work well together, if you're willing to replay the game.

- YS I & II: The games that started it all! They're not my ultimate pick because of the outdated mechanics and high difficulty limiting their accessibility, but all the strong foundations of the future series are there! All the details I love are already there, like the journal with fun 1-paragraph character descriptions, the weapons and armors grid display, the satisfying progression, the killer soundtrack and so on.

- YS IV: MEMORIES OF CELCETA: I love Ys IV, its setting and the organic progression of the plot. Compared to "old Ys", this is one of the longer modern party-based entries, where you control more than one character. It is a re-imagining of an older Ys IV from the 90's, and as such it is the technical successor of Ys Seven.

- YS IX: MONSTRUM NOX: One of the very best in the series, with very strong setting and characters, bringing a surprisingly good story to life. I don't recommend playing it first even if you totally can, since it contains an amazing amount of references to previous games. It is a strong standalone game but is best enjoyed with a deep knowledge of the series.


**SHOULD-PLAY TIER
- YS VI: ARK OF NAPISHTIM: I was surprised how much I enjoyed Ys 6, as it was released a while ago and is technically weaker than Origin and Oath in Felghana, but it has a very strong setting and story. It's not "must-play" for me because of its somewhat unbalanced progression, some plot holes in an otherwise excellent story, and a bland endgame boss.

- YS VIII: LACRIMOSA OF DANA: an absolutely amazing game almost to the very end, until its story and mechanics both crumble under their own weight. It is still very enjoyable and displays all the great qualities of the series, but my interest plummeted sharply during the last hours of grinding and narrative twists. Best soundtrack of the series!

- YS: OATH IN FELGHANA: I don't love this one as much as other people do, but it is a very nice game if you already have love for the series. The unbalanced progression and unfair boss difficulty prevents it from being an instant recommendation for me, but it's also a great reimagining of the old Ys III: Wanderers from Ys on SNES.

- YS SEVEN: I honestly thought I would hate this one, but I was wrong! I love that it comes right after the Ys VI story, including some recurring characters. It is the first of the party-based era of "modern Ys", with somewhat rough but efficient mechanics, and your friend Dogi the wall-breaker as a playable character for the first time! Even with a lot of clichés all around the place, it is still a strong and very satisfying entry.