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 Siddal-Vicag, Demon of Cruelty.
Defeat Xainal-Tarag, Demon of Apostasy.
Complete ten side-quests.
Defeat Tanhal-Arag, Demon of Loneliness.
Acquire 200,000 Gold.
Get Splendora to join your party.
Complete five side-quests.
Defeat Yatmal-Sadag, Demon of Deceit.
Complete one side-quest.
Acquire 5000 Gold.
Play one New Game for 1 hour.