@beperov
The objective of most rivals in romance manga is to serve as a roadblock, or to sabotage the main characters relationship entirely, often forcing the MC's into almost always contrived situations and dilemma's creating artificial drama in order to prolong the plot, while the "rivals", here, if they can even be called that in this manga, have done neither. Instead they have actually been quite helpful in helping the main characters recognize their own character flaws and shortcomings. So yes I do feel that the rival trope was subverted in this case, in fact it's probably more fair to say that there are simply no true rivals in this manga at all.
@JustNatsuki
A huge bowl of just Monika