This name is very much not the right one, as "Otona no Maki" is simply a subtitle appended to chapters of this story dealing with the adult characters (only 4 out of the 41 collected here). Every chapter has a different subtitle of this kind and the bulk of the series very plainly does not deal with adults, so it would seem fairly evident to the least amount of investigation that this is not the overall title, yet multiple sources persistently list it as such.
I feel bad when I read a chapter that focuses on an anime season 2+ school group. I just can't get into those chapters. I don't feel like I've been exposed to those characters and their backstories enough to care. Maybe I should start reading the mainline manga series to get to know them better.