Here is the full list of all 20 Hentai Story achievements.
Collect all pictures from Jessica
Collect all pictures from Katie
Assemble the first picture with Jessica
Collect all pictures from Hannah
Assemble the first picture with Katie
Collect all pictures from Eva
Assemble the first picture with Hannah
Collect all pictures from Daysy
Assemble the first picture with Eva
Collect all pictures from Maddison
Assemble the first picture with Daysy
Collect all pictures from Rose
Assemble the first picture with Maddison
Collect all pictures from Violet
Assemble the first picture with Rose
Collect all pictures from Emily
Assemble the first picture with Violet
Collect all pictures from Alice
Assemble the first picture with Alice
Assemble the first picture with Emily