Klefki can be obtained before the fight with Adrienn instead of before Titania as the document suggests.
It should also be noted that in order to get the classified information, you need to return a diamond ring, which can be found while diving in Azurine Lake.
Can't remember exactly which dive spot it was, and I can't remember if you need to find the key for it.
There's also a battle when returning the classified information to
And the difficult battle is more specifically a double battle