Here is the full list of all 42 White Day: A Labyrinth Named School achievements.
Hidden Love
Forgive Me
Experience Death 10 Times
Clear Normal Mode
Friendship
Arrive at the Bottomless Pit
Visit the Labyrinth
Arrive at the Auditorium
Each Encounter is a Surprise
Woman living in a cabinet
Experience Death for the First Time
I'm Perfectly Fine
Arrive at the New Building
Head Ghost Has Nice Hair
Delicious Soy Milk
Arrive at Main Building 2
Enter Main Building 1
Experience Death 50 Times
Experience Death 100 Times
Clear Very Easy Mode
Clear Easy Mode
Clear Hard Mode
Clear Hell Mode
Clear Hell Mode 7 Times
Clear Hell Mode 10 Times
Truth
Dangerous Pleasure
Hipocrisy
Sincerity
Tired of Love
You Are Mine
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
You Can't Do this
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