A veeeeeery fast paced manga, and since most of the focus is on the female character, my guess is the author ran out of time to do the male character's background. You could say it's unrealistic as well, and the side characters aren't even that much. A light read, if you may.
The main characters are pretty cute. Although I did find the age gap a turn-off, the story is so unrealistic and basic it didn't even incite that much rage in me.
It was interesting, however, seeing the author, Yamazaki Kore, transition from this kind of mindless seinen writing onto the masterpiece that is MNY.