Firework

All Achievement in this game are for completing chapters, and so are story related.
This achievement is for completing the Chapter 7, Incinerate.
Chapter 7 is a very short chapter, also the last chapter before epilogue.

I found that after completing each chapter and doing alt+Tab to go on other screen will force the achievements to pop up after a few seconds.
Achievement Timestamps:
00:00:00 - Prologue: Debt
00:09:00 - "Devil within" Achievement
00:09:10 - Chapter 1: The Telephone
00:28:40 - "Splendid night view" Achievement
00:28:50 - Chapter 2: Accumulated Sins (I)
00:43:30 - "Father's debts paid by son" Achievement
00:43:40 - Chapter 3: Accumulated Sins (II)
01:01:50 - "Fangfang's wonderland" Achievement
01:02:00 - Chapter 4: Accumulated Sins (III)
01:27:05 - "Come back, my son" Achievement
01:27:15 - Chapter 5: The Bird
01:40:20 - "Be a bird" Achievement
01:40:35 - Chapter 6: Milky Way
01:44:55 - "Milky Way" Achievement
01:45:00 - Chapter 7: Incinerate
01:56:20 - "Mountains of ashes" Achievement
01:56:30 - Epilogue: Like Tears in Rain
01:58:20 - "Like tears in rain" Achievement
Let the Credits run for the next achievement. Don't press any buttons.
01:58:30 - "A cold parting dream tonight" Achievement
01:58:40 - Subscribe!

This unlocks for completing Chapter 7. Firework is a horror puzzle game, that requires you to interact with the environment to collect clues and solve puzzles (similar to a point and click adventure). There is one major puzzle in Chapter 7. It is important to note that the game will not allow you to solve puzzles until you found the required clues, which is why a video guide is provided.



Here is a full video walkthrough, including all achievements and puzzle solutions! (Timestamps in YouTube Description)