No one gave the series the doujins it deserved so the author did it himself. What a chad.
That being said, I honestly wouldn't mind more manga with full hentai elements. There's a gaping whole where the niche would be and the few things that fill it right are absurdly sparse or absurdly short...
Thats progress baby! I ended up binging this whole thing in one night, its awesome!
Also why did that fish guy never report on what masturbating while counting prime numbers was like?