Here is the full list of all 16 Black Closet achievements.
Win the final conflict with four minions on the Student Council
Unlock All CGs in both art sets
Win the final conflict with three minions on the Student Council
Win the final conflict with only two minions left on the Student Council
The seats recline so that you can look at the stars....
Your Queen has been poisoned by the Red Mask Society. Must have been those chocolates.
She's straight, but not rigid.
As long as you're both adults...
One of your minions has gotten a little too possessive.
You have graduated from St. Claudine's.
You have kissed (or been kissed by) a freshman.
You infiltrated the Red Mask Society in order to betray them
You have been fully initiated into the Red Mask Society.
You have used a minion as your own personal slave.
You have run a lemonade stand.
You have managed to win a traitorous minion back to your side.