Recent discussion of this game on RFN has me even more interested, though the session stuff seems a bit odd to me. If the weapon triangle exists and there's a lot of variation in the party, why would you want people to start sessions with you? Maybe for consecutive weak point strikes, even when you're inputting for a character with a weapon weakness? It's a bit odd, but I'm sure we'll find out more.
Glad to hear that it's also a lot darker than it was initially portrayed. The pop idol industry may look pretty, but there's definitely disenchantment to be found there.