Here is the full list of all 21 Prison Princess achievements.
Escape Zena's Dungeon.
Escape Aria's Dungeon.
Get Zena off the statue, stat!
Get Aria out of the statue, post-haste!
Race to get Zena off the statue again.
Quickly get Aria out of the statue again.
Escape the sofa trap in a flash.
Obtain the Shining Liquid in a jiffy.
Nimbly get out of the bathtub.
Speedily solve the pedestal puzzle.
Obtain the Sacred Sword.
Obtain the Sacred Goblet.
Obtain both of their shackles.
Obtain the Forbidden Book of Poetry.
Obtain a very Naughty Book.
Obtain the Essay on Beauty.
Ending 1/5: Complete the normal route.
Ending 2/5: Complete Zena's route.
Ending 3/5: Complete Aria's route.
Ending 4/5: Complete the Demon King route.
Ending 5/5: Complete the true ending.