So the villain was not really evil
I dont understand why would people think she would be anything but a antagonist since this is the 3d time it happens and with the father I can guess he cant be since the series would be over but with the Twin Stars it was very obvious the way it was immediate defused this isnt the kind of story.
We have antagonists that have their own goals that dont exist solely to create drama, they provide obstacles for then to overcome ... the father so they have goals to achieve, the Twin Stars ended up being a gag were the sisters got really upset but they ended not being even antagonists and the Principal so we could have another side couple as well developing Yuu beyond being a "stay at home husband" as well the General Studies Class.
This manga is pretty much a comedy seeing the sisters overreactions, the romance exists mostly as a driving force without every delving into
drama ... having "generic shoujo villain" doesnt really work since the tone is off and yes, nothing will advance not because "milking" but because this series is foremost a comedy, if all people want is to see "who wins" then they better off reading series that only have 4 volumes or just wait until its over and they can skip right to the end because they dont want to read it for what it is, a comedy.