I just picked it up today and I’m enjoying as I did as I first played it. However, after going through Lesson and Challenge Mode, it was rather confusing for me, so I do not know where to start. I have chosen three characters: Mitsuru, Yukiko, and Chie in that order. Because I’m not very familiar with 2D fighters, I would like to know what is the best character to start out with and comparisons/differences between them. Ultimately, knowing where to start is my first priority, characters second.
Unlike you, I’m experienced with 2D fighters - like you, though, I’m not very experienced with this game, at all.
I’ve dabbled with this and other Arc System Works fighters but never really put in the time with them to really know what I’m doing. For some reason I decided to pick this one back up after barely playing it after release - it got lost in the shuffle - but I like it so I want to at least get down the basics of it.
Thus far what I’d really suggest based on what little time I’ve put in with the game so far, is going into training mode and working on getting your character’s movement down smooth. Air dashes, jump cancels, dash cancels, multiple jumps, turning around in the air, etc etc. Worry about that stuff before worrying about the character specifics and combos and such. From what I’ve seen fluid movement is really key. Or not 
Perhaps a more experienced player can offer better advice!
:eek: First thing I would do is to familiarize yourself with the engine.
Learning how to move (airdashing, evasive action, etc.), what options you have in what circumstances (which actions you can perform after super jump, not being able to backdash on wakeup, etc.) and learning about the nuance mechanics like bursting and counterhits. It all sounds extremely basic, but they are important things that don’t change regardless of your character choice.
I would start with this before learning combos and super sick setups and damage and all that stuff. That stuff is good, don’t get it twisted, but learning the ins and outs of the game are essential. If you haven’t checked out the Dustloop wiki for P4U, please do so. Don’t worry about the character sections for now, but check out the system mechanics and make sure you understand what’s transpiring as you’re playing.
Once you do that and are ready to delve into characters, I would recommend Chie or Narukami as a starting point and branching out from there just to get accustomed to the way characters interact with the mechanics I’ve been fawning over so much. When you get comfortable with your character and learning their nuances (roll length, hitbox size, etc.), then you should start learning two different BnBs; one from a grounded hit and one from an air-to-air or an anti-air. They don’t have to do amazing damage, but they should be consistent sources of damage for you to tag your opponent with when you land a hit. You can learn the beefy combos later, you just want consistency at this point.
Once you’ve reached this level, you will then be able to move on to more advanced things like oki setups, tech traps and really have CH/FC combos.