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