Here is the full list of all 69 Angel Wings achievements.
Unlock Nuri's Good Ending
Unlock all Nuri outfits
Control your emotions
Unlock Nuri's Medium Ending
Fight!
Go skating
Party time!
Unlock Yujeong's Good Ending
Attend the work party
Buy some food
Eat ramen with Yujeong
Choose to help Yujeong
Receive the sheet music
Unlock Yujeong's Medium Ending
Eat salad together
Choose stealth mode
Complete the work assignment
Enter the bar
Select the Hierophant card
Select the World card
Meet Nuri
Begin a Route Selection campaign
Complete any route
Complete the game once
Unlock all Seola outfits
Unlock Seola's Medium Ending
Defeat Kaori
Play video games together
Win a basketball game
Help out with cooking
Eat chicken together
Go to the forest together
Attend the beach
Complete the lake run
Take a coffee break
Go to the mall with Chaeng
Stick around for extra practice
Visit the phone shop
Complete an activity with Seola
Leave class early
Complete an activity with Yujeong
Select the Hermit card
Pick up the phone
Check the computer
Unlock Kei's ending
Unlock all Kei outfits
Watch drama together
Give Chaeng the phone
Unlock Chaeng's Medium Ending
Unlock Chaeng's Good Ending
Unlock all Chaeng outfits
Jump into the hotel pool
Unlock Hyedong's Medium Ending
Unlock Hyedong's Good Ending
Unlock all Hyedong outfits
Unlock Jei's Medium Ending
Unlock Jei's Good Ending
Unlock all Jei outfits
Follow Jihyun
Unlock all Yujeong outfits
Enter the drum studio
Unlock all outfits
Complete all routes
Reject the current timeline
Tell Jei the truth
Unlock Seola's Good Ending
Complete the band
Unlock Yuri's Ending
Unlock the true ending