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