Hey MKRU, i've found a bug, let me explain.
When you read the story of bianca in the diary and once u get vampire power, u can transform into bat but the skin of bianca will not change BUT when u have finished the diary it is mila with the skin of the bat and its impossible to go back to the skin of Mila. My english is not perfect and i hope u will understand what i try to explain. as i can see it is not broking my safe or anything in the game. :)