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