Here is the full list of all 11 SEXTS achievements. It takes around 0-1 hour to unlock all of the achievements on Windows.
Finish a level in Very Hard!
Save a picture in the gallery
Collect 10 maids!
Collect 10 animal girls!
Collect 10 witches!
500 letters written!
You missed 5 times!
Complete 25 words!
100 letters written!
Complete 10 words!
Start your first game!