I think from the lack of fanservice, it's not quite right to call it a doujin.
The whole story in the spin off this time in my opinion is like the main manga which is filled with comedy with a bit of fanservice (which is getting less and less). For the character design itself, it's good not to change.
Overall, I think this spin off manga is quite interesting to read in terms of a simple story, although not much different from the original manga.
