[ The creak puts him immediately on guard the sword at his side not being drawn quite yet but he will grip its handle as his eyes narrow. The books he was flipping through are placed back in the bookshelf as he turns to regard the others.

He'll look down at the keys in his hand before nodding. The desk might prove to have useful information, true, but now with the unknown noise he's not sure if it's wise to open it. ]

There is a door here as well. However I do not know if it is safe to open it. [ Then again getting stuck in this place, almost like a cage in its lack of doors, was far worse. ]

I will come with you to investigate. [ He'll direct his attention to Nanoha as he holds out the keys for Inaba to take. ] ...if it becomes too dangerous please use these to open the door and get away.