Here is the full list of all 15 The Princess' Heart achievements.
Play one New Game for 15 hours.
Play one New Game for 10 hours.
Finish the game!
Defeat Izdul-Kalag, Demon of Desire.
Defeat Xainal-Tarag, Demon of Apostasy.
Complete ten side-quests.
Defeat Siddal-Vicag, Demon of Cruelty.
Acquire 200,000 Gold.
Defeat Tanhal-Arag, Demon of Loneliness.
Defeat Yatmal-Sadag, Demon of Deceit.
Complete five side-quests.
Complete one side-quest.
Get Splendora to join your party.
Acquire 5000 Gold.
Play one New Game for 1 hour.