Here is the full list of all 18 Reach 50 : Sexy Hentai Girls achievements.
Unlock the character #2
Unlock the character #3
Unlock the character #4
Unlock the character #5
Unlock the character #6
Unlock the character #7
Unlock the character #8
Unlock all the outfits of the character #1
Unlock all the outfits of the character #2
Unlock all the outfits of the character #3
Unlock all the outfits of the character #4
Unlock all the outfits of the character #5
Unlock all the outfits of the character #6
Unlock all the outfits of the character #7
Unlock all the outfits of the character #8
Win 10 games
Win 20 games
Win 50 games