Here is the full list of all 21 CAFE 0 ~The Drowned Mermaid~ achievements. It takes around 0-1 hour to unlock all of the achievements on Windows.
You have unlocked all of the achievements.
You have cleared the extra bonus!
You have unlocked all of the CGs.
You have cleared the prologue!
You have unlocked the Bad Ending.
You have unlocked the True Ending!
You have regained all parts of the Original Heroine!
Sui finally cast his magic on you.
You remembered what actually happened.
They shall get what they deserve!
You have unlocked Shou - Evil Ending!
You have unlocked Shou - Good Ending!
You have unlocked Tooru - Evil Ending!
You have unlocked Tooru - Good Ending!
You have regained all parts of the Good Heroine!
You have regained all parts of the Evil Heroine!
You got your chest back!
You got your head back!
You got your stomach back!
You got your legs back!
You got your arms back!