Here is the full list of all 17 Hentai Oppai achievements.
Have you tried to type "h" 3 times in game?(Complete all Level)
Complete Level 6
Complete Level 7
Complete Level 8
Complete Level 9
Complete Level 10
Complete Level 11
Complete Level 12
Complete Level 13
Complete Level 14
Complete Level 15
Complete Level 16
Complete Level 5
Complete Level 4
Complete Level 3
Complete Level 2
Complete Level 1