I was contemplating making a thread about this but looks like someone already did it. And I'm really surprised at how many positive responses there are. Only other comments I've read elsewhere have them comparing this series to Akaboshi and deciding Medaka Box to be mediocre and Akaboshi to be very promising.
Well, Akaboshi totally feels like another Naruto or One Piece so no duh there.
Either case, I was expecting way more criticism.
Now I dunno about a male rival. Medaka is so superhuman that pretty much any other guy might feel way too intimidated to try to live up to her standards. I do predict a super male will show up at some point and try to impress her with equally superhuman traits and abilities, although all it really takes is to be genuinely concerned for her as a human being as Zenkichi does. And Medaka utterly trouncing the super male in the end anyway.
I think the beauty of this manga so far isn't about finding out if Medaka has a weakness, but about how could someone so flawlessly perfect as Medaka see anything of worth in someone as ordinary as Zenkichi. We would get an extremely emo and unconfident male lead in any other manga, but Zenkichi looks to be thankfully different.