Here is the full list of all 15 Hentai Lover's Train achievements. It takes around 0-1 hour to unlock all of the achievements on Windows.
Fifteenth girl
Fourteenth girl
Thirteenth girl
Twelfth girl
Eleventh girl
Tenth girl
Ninth girl
Eighth girl
Seventh girl
Sixth girl
Fifth girl
Fourth girl
Third girl
Second girl
First girl