Gah, this is just like Rosario Vampire, or heck, most recently, Komi-san wherein the MC is pretty much shown to be interested only in one person (FMC) there's clearly no chance in gaining his attention. Get's one wondering what's the point in having the harem then.
Not dissing on Not-Mash, she top tier, just this kind of development feels wasted, atleast to me. And kind of feel bad for the other candidates, no chance at all... Like this girl here and Manbagi!