I already figured out Mira was Aku in Chapter 3.That was rather obvious...
Hmm... you are right about Princess Aku being impersonated, but you've got the wrong impersonator.
Hint: Given enough makeup and practice, a young person can easily pass themselves off as being middle-aged... and as of right now, Whetu Kealoha and Yukiko Takahashi are both unaccounted for.
I'm planning to post the new chapter around 5:00pm Eastern Daylight Time, (gotta get some screenshots) and I've just now added an extra line of narration to it that should give away which member of Kendra's government is being impersonated by Mira. You, the reader, should be able to spot Mira by the time the chapter is over, even though she won't be unmasked. Happy hunting!