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