Responses
The rest are original doujin. only page 43-48 are from Official Novel 5 scene.
Where do you read the novel?
You can check through " Yokozawa Takafumi no Baai" on pressbook. They have 6 volume total.
All translated in English by September Scanlations.
Here's volume 1. For vol 2, change the num ytnb01 to 02 etc.
https://ytnb01.pressbooks.com
I believes, this doujinshi is redraw version from the novel. Started from chapter 43 till 48. I just read it on the novel. I m not sure about the rest, since i have finished reading the novel a very long time ago.