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