Folks having trouble with FINAL BOSS, read this

While Orange soul first seems similar to Yellow, the core problem in orangis is not aiming but TIMING. Unlike yellow, charging does nothing other than giving more grace for the timing, but it often screws you up more than it helps you due to the start and end lag. So do NOT hold Z, and learn to time properly.

If tap Z is not working, you are most likely tapping too late. Look at the gray bars. You need to tap Z just before one bar's spacing. (imo, this should be telegraphed more clearly at the start of the battle) For Flowery, tap Z at Za... "uh!" (or "Orange!") to parry, although this does not crit.

Yes, Orange soul has a crit which gives +6 extra TP in addition to the base +7 when parrying Flowery (or Orange), like how Green soul also does. I personally haven't been able to get the proper crit timing without charging though.