Harmony: The Fall of Reverie

There are multiple paths to unlocking this achievement, this is the one I used:

Act 5, Chapter 1
The opening decisions will be different depending on your choices in the previous Acts, but at some point you'll get to an option called "A Forbidden Feeling". From there choose:

• Open up about Brittle
• Talk about Reverie
• A call to reality
• I'll leave
• End of chapter

Act 5, Chapter 2
Nothing matters here, choose whatever you want

Act 5, Chapter 3

• On the edges of fate
• The final countdown
• Pick either decision, one will be locked based on earlier choices but it doesn't matter
• The end has come
• Pick either decision, one will be locked based on earlier choices but it doesn't matter
• Pick all the Goodbyes until you can progress on
• Where's Nora?
• Pick whichever Goodbye Nora is available, doesn't matter which
• Pick either decision, doesn't matter which
• Hold back the night
• Goodbye Harmony
• End of chapter

Achievement unlocked!