I was gonna play that, how's it like? I played the PS4 game and loved every minute of it, then went to play the PSP game but got stuck on level 2-2, the level just never ends...
As it seems, if I enable cheats once (wither used them or not) it corrupts the game save permanently and you cannot progress past 2-1, you need to completely erase your save in order to fix this, but the boss in 1-5 is a bit too difficult and since I can't read Japanese and afaik there is no English translation I dunno how to heal properly, it's a shame as the game is quite fun but the language barrier ruined it for me.
Onechanbara Special, the PSP one.
It's the only one in the series that uses a real time menu, circle (if I remember correctly) bring up this menu where you select items to use and can even change weapons this way (if I can remember correctly).
The PS2 games are more or less budget DMC clones, the first game simplifies the combat system that DMC introduces, no weapon switching (until the 3rd game on xbox360), you level up like it's an action RPG with distributable points to your stats.
Like DMC there is a secondary combo but it's timed and very strict with it's timing compaired to later games in the series.
You level up by collecting yellow orbs from dead enemies, the size of these orbs is tied to your current hit count.
Unlike DMC where you prioritize style over everything else, this takes a page from Ninja Gaiden where you stack up hit counts, rolling can extend this to keep the count on screen longer.
You might need this because unlike other action games, the 1st game doesn't have a long range attack, instead you have kicks and a suicide attack (equivalent to holy water in DMC).
This lower part might not be nesseary to say since you played the PS4 game, but I'll include it in my post anyway..
The twist in gameplay is that you also manage blood guages, one for your body and another for your weapon.
The more blood on your weapon the slower your attacks are and at full can get stuck in enemies.
The more enemies you kill with your sword, the more blood gets on your body, if you fill the guage you go berserk, stronger and faster but your health drains slowly and can kill you.
Kicks don't get blood on you as much but are weaker, finally suicide is tied to the circle button (only in the 1st game), it's like holy water in DMC but only affects nearby enemies that you see on screen. Suicide attacks consume health so watch out for that since it's too easy to trigger in the 1st game.
Overall the 1st game has a lot of issues, but there's a proof of concept for a good game inside it, if you can look past it's flaws.
