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