Here is the full list of all 20 If My Heart Had Wings achievements.
Fail to complete any route.
Complete all routes.
Complete the Yoru route.
Watch all of the cutscenes.
Complete the Asa route.
Watch 80% of the cutscenes.
Complete the Ageha route.
Open the gallery.
Complete the Amane route.
Watch 60% of the cutscenes.
Complete the game for the first time.
Complete the Kotori route.
Watch the ending movie.
Watch 40% of the cutscenes.
Watch 20% of the cutscenes.
Watch the second opening movie.
Finish the common routes.
Watch the first opening movie.
Watch a cutscene for the first time.
Start the game.