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