I have a little over 50 substories done and to be honest, a vast majority of them is exactly like the ones from 1/Kiwami, forgettable fluff that is only good for some money and a few EXP.
Every boss I fought so far was kinda garbage, not really difficult, just annoying. Combat against regular enemies is fine though.
The story is kinda middle of the road for the series, really dumb twists and motivations, contrieved melodrama, somewhat naive, but you're still somehow invested in the characters. The usual. I'm in chapter 11 right now, so stuff is happening.