this had shown up here on nyaa some years ago, and I had saved a copy of it I do not know if the "collected edition" is going to include it it is the prequel story set in the Taisho Era it was assembled in to tankoubon style vols DDL https://mega.nz/file/AggXAQ7Y#08oH0lOmGlNImtbhy20zo1H5C3W0Uy0yBiZ-Aph1SqU