The password is the symmetric key used to encrypt the backup and I am not aware of any tool that will help you. There are password guessing utilities such as JtR or Hashcat, but they need a hash to work with. Since Aoemi isn't a common system to crack there are no helper XtoJohn utility scripts that I'm aware of.
If you can script at all and aoemi has a cli tool for decrypting you could hunt for a utility that generates permuations of words (assuming you have an idea of the password or it's length) you could generate a list and feed it to a custom script (assuming there is a cli method to decrypt a backup)
