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