It is an original manga. Dj authors do make original stories whenever they can or want to. To mangaka of Given used to create IwaOi djs before starting Given
I understand that, as a fanfic writer. What I mean is that is a derivative work, when I read it I liked it so much and still hadn't seen the anime that it didn't go through my mind that it was a dj. I don't underestimate an artist who works with characters not their own but I understand what you say. I'm sorry I sounded condescending.
Wait I think you're misunderstanding something because this manga is in fact original. These are brand new characters from the author, just that they happen to look like Hinata & Kageyama because the author likes KageHina and has drawn KageHina djs in the past. But this series is 100% original.
I always thought that this was an original manga XD
A few years later I see the notification and I noticed that is not XDXDXDXD