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