Here is the full list of all 30 Once on a windswept night achievements. It takes around 1-2 hours to unlock all of the achievements on Windows.
Arrange the actors back on the stage.
Wait for a play that's already over.
Reach your happy ending.
Return to the library when Lycoris needs you the most.
You remember who you are.
Read a lonely spirit's story.
Bring the story to a premature close.
Profess your love for Madeleine.
Profess your love for Daffodil.
Read Daffodil's story.
Offer Daffodil a few too many compliments.
Learn Lycoris' favourite flavour of tea.
The traveller refuses to tell Daffodil the truth.
Answer Lycrois' question incorrectly.
Try to steal Lycoris' most precious possession.
Take the traveller's name for your own.
Name yourself after a certain flower.
Multiply the number of daffodils in the story.
Listen to a mysterious voice.
The traveller leaves the church early.
Lycoris gets a little too possessive.
Read Madeleine's story.
D-Did you just insult a girl's cooking?! You monster!
Let yourself forget everything.
Return to the library for a second time.
Madeleine refuses to share her story.
Throw caution to the wind!
Start a new story.
Make yourself the third Madeleine.
Lycoris welcomes you to her library.