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