Here is the full list of all 30 Hentai Melody achievements. It takes around 0-1 hour to unlock all of the achievements on Windows.
Complete 1 level
Complete 2 level
Complete 3 level
Complete 4 level
Complete 5 level
Complete 6 level
Complete 7 level
Complete 8 level
Complete 9 level
Complete 10 level
Complete 11 level
Complete 12 level
Complete 13 level
Complete 14 level
Complete 15 level
Complete 16 level
Complete 17 level
Complete 18 level
Complete 19 level
Complete 20 level
Complete 21 level
Complete 22 level
Complete 23 level
Complete 24 level
Complete 25 level
Complete 26 level
Complete 27 level
Complete 28 level
Complete 29 level
Complete 30 level