2.0
If you go too fast and simply follow the main quest, without doing side content, you'll go from level 21 to 23, skipping level 22, and skipping the introduction to the card system permanently, bricking your character because you'll be forever missing one of the key component to your character's power
Oh and you can't delete your character btw, or if you can, it' so well hidden I couldn't find it on the login screen or options in game
Edit: Oh and if you link with a qoo account, you don't get access to customer service to let them know that something went wrong (tbh, haven't tried with another account that isn't qoo to see if it's just a qoo problem, but tbh, I don't care anymore, avoid that shit like the plague)