So here's a few of the problems:
1. it is so incredibly accidentally missable if you're just running through the story. remember, miss one and you'll screw the ending
2. what the hell is 'Dry Sonata'? It doesn't tell you if it's a regular skill (the upgrade tree is like 400 tiny dots for each character, I went trolling through a lot of them) or something else. It's apparently a chain skill which they teach you about in a tutorial in chapter 3. Great!
3. wait, I can't tell how to do 'Dry Sonata' even if I've guessed that it's a chain skill, it's not in any lists that I can find. I hadn't paid attention to the tutorials so I thought maybe I'd get it by leveling up - I didn't. If I had paid attention I maybe could've taken a leap and surmised that it's on some sort of collectible. maybe something called an 'expansion disc'.
4. I have no direction as to where the expansion disc is! I'll go back and read the quest info. I think he said something about how I should train some more (this is why I thought it was related to leveling up). Turns out that it isn't in any of the explorable areas but rather in the 'Training Room' that's inside your main headquarters. Wonderful!
5. Where the

is it in this training room? There's 10 rooms blocked by blare force fields, some of them say that you need some random monster item drops to pass. Ok? So I would need to try and find the right items to open all of the force fields to find the right room? Even assuming I could've guessed that I need to go to the far western room, I need to get two 'spike' items of some sort. Alright, I'll get em!
6. wait - what drops a spike item????? GAHHHH
7. Oh, there's a scorpion looking thing in this mob! Maybe he does!
8. (kill like 10 scorpions, no drops)
9. GAAHHHHHHHH
10. (the 11th one drops one spike)
11. phew! one more to go!
12. (more fights, get one more spike)
13. ok, now I can go in to the room with the expansion disc to unlock the skill to be able to do 'Dry Sonata'! Almost done!
14. ...
15. you mean I have to get different weapons and unlock new skills for the characters before I can actually do 'Dry Sonata'???
I already had the money and skill points to be able to get all the stuff, don't worry. I didn't kill my neighbors or anything and with the guide info this really only took like 30 minutes. of course now I can't figure out how to end the

ing chapter so I wasn't really in that much danger of missing it. I'm still having fun with the game though, I swear! I'll just always have the sidequest guide handy.