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