Ys 5 is the one entry in the Ys series not (at this time) translated into English in any form whatsoever, be it official or fan-made. So there's a gap in the story here for those of us that don't speak Japanese, as Ark of Napishtim is Ys 6. Apparently during the course of Ys 5, Adol acquired a pirate ship and some pirate wench, at least according to the usual jump-cut-filled anime montage that starts this one out ... said pirate ship also got attacked, sunk, and Adol washes up on another remote island full of demonic troubles in typical Adol style.
Ys 6 is also a revival of the series from a decade of dormancy; this first came out for Japanese PCs in 2003, while Ys 5 was a SNES game from the early-mid 90s somewhere. It's actually a port of a port, as the game first appeared in English as a PS2 port, and the PSP version is a slightly scaled-down port of that port.
Unfortunately, being a 2003 release, that means we're still firmly in the era of early, clunky, unrefined 3D platforming with a lot of low-detail and unappealing textures and such. The game uses the same engine that later release Oath in Felghana does, but it seems more poorly implemented here. This engine continues the shift from the "bump combat" of Ys I-II and IV to a more Zelda-ish action-oriented top-down-view style started by Ys V, but now with quasi-3D field of play. Unfortunately, the quasi-3D is a problem; aside from using kind of crummy textures and not looking all that good, it creates a depth perception problem that makes jumping around and pinpointing exactly where you are in relation to a flying enemy a bit iffy. This was a bit of a problem in Oath in Felghana too, but it was de-emphasized there by not making you do a lot of precision platform jumping and not going too hard in da paint with the flying enemies. Neither of those things is true here. Dungeons are festivals of Finicky Platforming; usually you won't die if you fall, but you'll have to tediously clamber out of some basement room and jump back up to where you were for another go. And the bosses almost all seem to either float, fly, jump or otherwise do some airborne shit that makes it overly hard to line up with them. Adol's overexuberant slidiness when attacking (even the most basic swing sends him forward to some unpredictable degree) really doesn't help the platforming issues here either.
Other than the gameplay being dodgy at times, there are some other issues. In terms of the story and aesthetics the game seems awfully Generic Animu and uninspired for what was supposed to be a triumphant return from the grave for the series after nearly a decade. I mean, by the 6th game in a series you kind of expect some uninspired performance, but after a nearly 10 year break you'd think there would be some more enthusiasm and creative energy pulsing here. Instead it kind of feels like you're rotely going through the Ys Routine (gradually explore slightly mazey overworlds and dungeons connected to Hub Town while Grindan to be able to survive further-flung areas with tough enemies, also peck around for sometimes obtuse event flags) as cooked up by a bunch of marketroids. The game is also padded with heaps of repetitive, pointless walking through empty space for some unknown reason. There's too many stretches of these pointless copypasta'd rooms just to fill physical space, with no art to look at, no real purpose to them, no nothing. Even the music sounds like it's, like, the Ys fanfiction equivalent of music or whatever.
After 10 years most of the talent associated with a beloved franchise of the past has usually either moved on to other companies or been promoted up the ranks such that they aren't doing the grunt development work they became known for anymore, so you get a whole new team of noobs who can't quite capture the spirit and appeal of the original. I'm sure that's the case here and explains the Mehness and blandness ... but only two years later they would do a really good job with Oath in Felghana, so I'm not sure what happened here other than some intersection of noobness, low budget and possible laziness. Even with all that the game is still an alright action-platformer-adventure-RPGish thingy, but I feel like Ys could have been done much better justice than this after such a long absence. Also, apparently load times on the PSP are a major issue unless you install the entire thing to your memory stick.