https://www.dlsite.com/maniax/work/=/product_id/RJ003518.html

The entire work seems to be biographical, two doujins on the gallery were apparently unpublished (The Sakura one wasn't even finished) and there's a lot of sketch work; more of an artbook than anything. Also, it's about Nitta Jun but it's uploaded by Houseki Shounen's circle.

There's a lot of text and a Q&A, it's better if you try and read it yourself:
https://mega.nz/file/mCZnXahL#1WdvCMEBrQ9o6R4gLSNpwFKu4gqBCfwkL-XCaSFXcao