Uhh, guys I think that, for now at least, the trope was subverted. He is actually actively helping the main couple to be together. They did't seem to have any slightly romantic interaction as well. (But yes, is only the first chapter in which he appears, so things can change)
Even tho not so much as before, in Japan, mostly in the traditional families, arranged marriage is still a thing (omiai for example, for fucks sake, people still go to omiais). Respect to the elders and their desires is heavelly taken into account as well. Promises too, are very valued. So I don't doubt that this new boy will struggle to break off the marriage because of his grandpa, and even Alice.
The fact that she know nothing about love is actually well written, which is the difference between this history and many others shoujo. She is not some dumb dreamy girl. There is nothing forced nor cheesy. Besides, it took her about 4-6 chapters to realize she likes him, so is actually flowing pretty well.
Now, Im not saying that it won't end up as a fucking boring cliched trope, BUUUTTT, Im just gonna say by now that we should give the author a vote of confidence, cuz so far so good.