Here is the full list of all 17 Hentai Girl Division achievements.
Finish main story in Hardcore mode
Upgrade to maximum fire rate for at least one girl
Upgrade atleast one skill to max level
Watch every hentai scene
Beat all challenge mission
Kill 4000 enemy
Reach level 5 for all girl
Finish main story
Collect 5000 star
Talk with every girl when possible
Kill 100 elite enemy
Reach level 5 for atleast one girl
Reach level 3 for atleast one girl