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