As much as I like to talk about how emotional and wonderful the song is (like the fact you made this much emotion and storytelling in one single song is enough to be great), I would like to point out how well you analyzed the themes and how you presented it in such a clear and clean way with the board.
I can see how your thought process goes from the explanations and inspirations, mainly how you would think that the game would be a puzzle platformer with emotional storytelling like Celeste. The breakdown of even the title of the song "Tsuya" being part of your explanations show how well-researched are you to make this entire one song count. You did amazing with this track and you should be proud of it.
Now for music, I'm not sure where exactly you will put this in the game, would you put it at the climax of the story? the ending sequence of the game? you could even put it at the title screen as the main menu music lmao. Seeing how you talk and deconstruct the concepts is amazing and something I would strive for.
Amazing work, You deserve all the praise.