Here is the full list of all 69 Angel Wings achievements.
Enter the bar
Leave class early
Complete an activity with Yujeong
Select the Hermit card
Pick up the phone
Select the Hierophant card
Select the World card
Attend the beach
Visit the phone shop
Go to the forest together
Help out with cooking
Check the computer
Unlock Kei's ending
Unlock all Kei outfits
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
Attend the work party
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 Jei's Good Ending
Unlock all Jei outfits
Meet Nuri
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
Take a coffee break
Eat ramen with Yujeong
Choose to help Yujeong
Receive the sheet music
Unlock all Yujeong outfits
Enter the drum studio
Complete any route
Unlock all outfits
Begin a Route Selection campaign
Complete the game once
Complete all routes
Reject the current timeline
Tell Jei the truth
Party time!
Unlock all Nuri outfits
Unlock Seola's Good Ending
Unlock all Seola outfits
Play video games together
Unlock Yujeong's Medium Ending
Unlock Yujeong's Good Ending
Complete the band
Unlock Yuri's Ending
Defeat Kaori
Unlock the true ending