Need Helping Finding... the Cathedral of Sound

[IrregularPerson]

I believe it was a one-shot about how the last choir kid has grown up, the times have changed and the government has no need to continue the tradition of song. BUT panic- they find clues for why it's terribly important to continue that tradition. "They had to continue tradition lest they (the people) forget..." the cathedral was meticulously designed so that the songs of the choir kids would support the structure, as they rush back to sing, the place is already trembling, and as they've already grown up they can no longer sing the notes necessary (or the fact that they are the only one singing).
It was a beautiful oneshot and I would love to revisit it! Especially since I forgot if there even was an ending!

 

[Yatsuki]

@IrregularPerson Is it this one?
https://mangadex.org/title/16383/onkai-no-miyako

 

[IrregularPerson]

@Yatsuki THANKS YOU!