Where is the Second Treasury?

Ace enters the fourth floor with eyes full of anticipation. 

The fourth floor of the library was quite mundane, there was a wooden table and chair. And a small bookshelf that only has five old books. 

Ace quickly stores the books inside the thief's space and scans the wall behind the bookshelf that looks like a rusty old wall. Just as he thought he didn't find a thing! 

'This formation plate is also not connected with the treasury formation just like that old hag said.' Ace thought gravely. 'This is a problem, I can't find loopholes without true and false eyes, how I'm supposed to use treasure opening hands?'

Because treasure opening hands can only be used when he saw flaws with true and false eyes. These two skills were made for each other and with even one of them missing the other was useless as well.