Just hovering over the word "oni" produces the sound of crinkling plastic. It's actually somewhat beautiful.
Bread is uncountable, just like water. Loaves of bread, however, are countable.
I tried "the men have bread" and it was wrong, but Oni is meant to be used for men only, makes no sense since the plural of they(men) can also be The men
It's not "men only", it's "with at least one man". "Oni" may be a group of 99 women and 1 man.