Here is the full list of all 42 White Day: A Labyrinth Named School achievements.
You Are Mine
Experience Death 50 Times
Sincerity
Clear Hell Mode 7 Times
The Scent of the Bathroom is Becoming Heavenly
Tired of Love
Nothing Fazes Me Now
Dangerous Pleasure
Flirt with the Girls
Clear Hard Mode
Each Encounter is a Surprise
Clear Easy Mode
You Can't Do this
Friendship
Clear Hell Mode
Hee-min, Still a Growing Boy?
Complete the Ghost Collection
Collect All the Ghost Stories of Yeondu High School
Forgive Me
Truth
Clear Very Easy Mode
Arrive at the Bottomless Pit
Visit the Labyrinth
Encounter All the Ghosts in Yeondu High School
Woman living in a cabinet
Hipocrisy
Clear Normal Mode
Arrive at the Auditorium
I'm Perfectly Fine
Arrive at the New Building
Experience Death 10 Times
Arrive at Main Building 2
Head Ghost Has Nice Hair
Bathroom is Scary
Delicious Soy Milk
Experience Death for the First Time
Enter Main Building 1
Experience Death 100 Times
Clear Hell Mode 10 Times
Hidden Love
Complete the Ending Collection
She Approaches from Afar