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