If you boot it up they give you the order to play it in. There is only 1 problem and it's at the beginning. They tell you to watch 358/2 before playing 2
DO NOT DO THAT IT SPOILS A MAJOR PLOT IN PART 2

Play it in this order

1

Chain of memories

2

358/2 days

Welcome to the current state of Square Enix.

Ditto. If these were FFVII-style remakes, sure... but for a two-decade old franchise whose last release was half a decade ago... I'd consider $20.

Just wishlist and wait for Steam sale.

1.5 kind of makes sense. It holds Kingdom Hearts 1 and a remake of the GBA game that comes before Kingdom Hearts 2 (also comes with a the cutscenes of another game between 1 and 2). I guess they wanted to keep the naming similar because 2.5 comes with Kingdom Hearts 2 and...a prequel to every game... and a cutscene collection of some weird side game about an AI. They then released a bundle of both of these on PS4 which they named 1.5+2.5. 2.8 they were really scrambling. Because they wanted to release the rest of the games in some way before Kingdom Hearts 3 so that holds a sequel to Kingdom Hearts 2, A standalone demo for 3 and...a movie from the earliest part of the series that actually is a giant pit of questions with no answers which may or may not have been answered by the gacha. No idea.

Not only are the numbers weird, the games within the series (more than just the main 3) came out as exclusives to a wide variety of platforms. KH has such a bizarre history.

This isn't even the tip of the naming weirdness this series has.

I've seen an hour long video essay that focused entirely on how they named the games.

Yes. That is correct.

To the point where I legitimately thought it was a mockery of the series. Oof.

They don't care. They already got what they wanted.

Xenosaga first.

Being generous with this actual estimate, there's like 22 of them.