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