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