Yeah, I knew about the randomness, from people streaming the game last week/early this week, but didn't realize the costumes still had to be purchased with in-game coins. The grind for "costume parts" sounds atrocious, although I was assuming as much, after seeing some Japanese Twitter complaints.
This lack of player agency is what really has me expecting the eventual offer to unlock costumes with real money.
I’m not sure if the coins will be a huge issue. I’ve gotten a ton so far. There’s nothing to spend them on yet since you can only use them if all your costume parts get random assigned right to actually buy a costume.