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