What is a Junon Boy? Kotoishi Naru keeps on calling the main character a Junon Boy. He seems to take this as insulting. 

What is a Junon Boy and why does he dislike being called that?
Junon is a monthly Japanese fashion magazine primarily directed towards teenage girls and women. It began circulation in June 1973.


Source: Wikipedia

Given Junon super boy contest is a beauty contest I would guess, "Junon Boy" basically means "pretty boy".

The magazine hope page can be found at: http://www.junon-boy.jp/

I am basing my answer on research so perhaps some one else can confirm this, also I could not find any information of the meaning of maganize name alone, so again I am basing on the circumstances.