Here is the full list of all 40 OPUS: Echo of Starsong achievements.
Enter Chapter 4
Enter Chapter 2
Complete the game without failing once
Complete the game without resonating with the wrong starsong
Never been hit once by the space debris
Not listening to Kay's advice
Protect as Jun
Help to return a favor
Enter Chapter 1
Enter Chapter 3
Enter Chapter 5
Complete the game
Die twice in a playthrough
Complete the game in 8 hours
Completely run out of fuel twice
Complete all the East Ocean puzzles without any mistakes
Not getting hit once when landing on Banshee
Visit over 10 different locations
Visit over 30 different locaitons
Visit all locations
Visit over 10 locations in Thousand Peaks
Visit over 50 locations in Thousand Peaks
Visit all locations in Thousand Peaks
Read the message
Acquire over 3 Tales of Failure
Acquire over 20000 credits
Acquire over 20 items
Acquired over 100 items
Acquire all items
Fully deck out Red Chamber
Decided not to send out the letter
Be kind to Bones
Be honest to Eda
Shoot the dart 10 times
Thank Remi
Trust in Remi
Let Eda decide
Enter Chapter 2: Part Two
Enter Chapter 3: Part Two