So, if you want to know more about world building, different scenes that happening behind or in parallel the main series this is a good to read.
I'll give one example of simple things address by this, remember at Rimuru's Ascension as a Demon lord, we can't see Youm and his men, Eren, Kabal and Gido at the scene. This is both on manga and in anime, now trinity address those and explains that magicules density are higher than a normal human could handle, hence they are not in there.
Overall, since the story is around the 3 girls from different majin, we get a glimpse of how other demon lords domain works too. Which is really good
