Here is the full list of all 19 Love n Dream: Virtual Happiness achievements.
You unlock all character information
Maximum 5 impression level for white_Fox
Maxium 5 impression level for _Valerie_
Maximum 5 impression level for Fiona_23
Maximum 5 impression level for Lucky_Star
Maximum 5 impression level for Tinybubbles
Collect total 45 stars
Use Fiona_23 skill 5 times
Collect all items
Use _Valerie_ skill 5 times
Spend 6000 gold or more
Collect 20 items or more
Purchase maximum level 5 medal
Spend 3000 gold or more
Use Lucky_Star skill 5 times
Trigger evasion white_Fox passive skill 5 times
Purchase medal level 3 or above
Collect 10 stars or more
Use Tinybubbles skill 5 times or more