Here is the full list of all 26 Eternights achievements.
Reached max rank with yourself.
You went on all of Sia's dates.
You went on all of Yuna's dates.
You made a promise with Sia.
You made a promise with Min.
You retrieved the Stone.
Reach max rank with a Confidant.
You made a promise with Yuna.
You helped Min break through the second wall.
You scavenged 10 city items.
Now you know how to give proper piggyback rides.
You helped Yuna destroy the first wall.
You got creative with your hand.
You explored the city for the first time.
The start of a peculiar bond.
Escaped the shelter.
You awakened your new arm.
Earned all trophies.
You are a social butterfly.
Reach max rank with all your confidants.
You made a promise with Yohan.
Going out with 1 person only til the end.
Date every dateable character.
You went on all of Min's dates.
You went on all of Yohan's dates.
You went on all of Chani's dates.