You do realize that someone can be in love equally with more than one person, right? XD
Besides, this manga has not just one story in it, so the romance tag applies to the other stories as well.
feel free to think what makes you happy
This has nothing to do with 'thinking what makes you happy'. It's a fact and easily seen in relationships old and new, all across the world even.
Just because you yourself don't like it or understand it, doesn't mean it's not a rea thingl. Please keep that in mind.
woahhh I can't understand why there is the romance tag when it's a threesome and in this kind of tag 'not all' there is always this someone of 3 left aside. Saying this by respecting other people's thinking but I can't bring myself to read it because I hate 3p everyone have their own taste