I've been playing the vita version of this game and damn I haven't had this much fun with a game in a while. Unfortunately since I can't understand Japanese, story mode makes no sense but I get the general idea (festival that brings back dead shinobi for a while, Asuka's granny has a younger sexy form, etc...).
Tons of stages both old and new. They look very nice, are all bigger and more explorable which is great. There are these towers you have to find and destroy in many stages in order to unlock girls' heart missions so it forces you to explore these fun stages.
No more separate school "homes" or unique school chapters. There's 8 chapters and all 25 girls are included in no particular order (you could play a Hanzo girl in one mission and then the next could be a Hebijo girl). Heart missions are back though for all 25 girls which tells a small story unique to each of them like SV. The best news is that you can use any girl to play any mission in both story AND heart mode (the only catch is you must first beat that mission with the original girl). Also there are now 3 difficulties: easy, normal, and hard (for both story and heart missions).
In terms of gameplay, the girls' speed now greatly varies. Shinobi like Asuka and Kafuru are very fast while girls like Yomi and Hanabi are veeeery slow. The movesets however are very similar to the girls' SV counterparts. They also still have frantic mode, transformations, and 3 ninja arts (although now for L+O you don't need to have critically low health to use 5 scrolls). There are also times when another girl will be your ally and you can perform a tag attack with her. Honestly I forgot about this mechanic as soon as I learned it at the beginning but it is essentially like a ninja art and it doesn't use scrolls iirc. Cutscenes are now minimal for ninja arts and clothes destruction cutscene has been shortened which helps keep the flow of battle. In terms of the new girls: Renka is very quick and her drum beats have great range. Kafuru (my new favorite) is also quick with great projectiles and her dolphin provides both heavy moves and transportation for her with certain moves. Hanabi has powerful light moves but is painfully slow. Her fireworks give her some range and her charged heavy attack is fantastic but she requires a more defensive approach. Ryoki is pretty fast and uses her gun as both a sword and to shoot enemies with and she can throw her shield as a heavy attack. Then there's Jasmine (I haven't been able to play her older counterpart Sagyu). So the downside is she doesn't have a transformation meaning no opportunity to fully refill your health. However this woman is so OP. Close range is amazing when she whacks you with her pipe. She also has great long range and can move so quickly with her charged heavy attack that her enemies can't see her coming.
Multiplayer mode is fun especially since you don't have to play online or ad hoc (random CPU are assigned). Since the options are all in Japanese I've only been able to play one mode so far (where you just kill your opponents) but it's still fun.
Changing room has more clothes as well as color changes for outfits (4-5 color variations for most) and you have more options to differ what the girls wear in their normal getup vs when they're transformed. Also each of the 20 original girls have their unique swimsuit they wore in the OVA. There is also a diorama mode which I haven't really used since it's difficult to navigate however it's exactly like the PS4 except only 3 girls instead of 5 can be viewed. You can see them in actual environments or in front of a flat picture background that doesn't change. Girls' facial positions, body posture, and icon expressions (like an exclamation point, steam, floating hearts, etc...) can a be manipulated. You can move them anywhere in a given map. There are also special effects you can add to environments like lighting.
Music is still high in quality but I wish there was an option to choose old themes for the girls. Also I want the main theme from SV back as it was so epic. XD
Graphics have improved since SV. Girls no longer have those thick outlines, hair physics are better as well. My only true con for this game is the framerate. I knew it would be 30fps going in but it can get choppy at certain points. Usually when you're versing 2+ shinobi and there's a lot of projectiles flying around. After a while I have noticed it less and it has never impacted my gameplay. Still a disappointment though and I hope a future patch can improve it. From what I've heard, PS4 always runs at a consistent 60 fps with no issues.