Here is the full list of all 33 SoulSet achievements.
Unlocked Shira's True Ending
Read the whole thing!
Unlocked Apris' Bad Ending C
Unlocked Apris' Bad Ending B
Unlocked Apris' Bad Ending A
Unlocked Apris' Normal Ending
Unlocked Apris' True Ending
Unlocked Yvonne's Bad Ending A
Unlocked Yvonne's Normal Ending
Unlocked Yvonne's True Ending
Was he in there all along?
Unlocked Marco's Bad Ending A
Choose wisely, My Liege
Found all the Red Clues
Found all the Green Clues
Found all the Silver Clues
Found all the Orange Clues
Unlocked Marco's True Ending
Unlocked Shira's Bad Ending A
Unlocked Shira's Bad Ending B
Unlocked Shira's Normal Ending
Unlocked Shirr's Bad Ending A
Unlocked Shirr's Bad Ending B
Unlocked Shirr's Normal Ending
Unlocked Shirr's True Ending
Unlocked Feathor's Bad Ending A
Unlocked Feathor's Normal Ending
Unlocked Feathor's True Ending
Unlocked Verin's Bad Ending A
Unlocked Verin's Normal Ending
Unlocked Verin's True Ending
Unlocked Mariko's True Ending
Unlocked The Secret Ending