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