Okay, first of all, do you REALLY think your manga's going to be published in shonen jump? Are you really so convinced that your manga idea's going to be picked up by one of the largest manga publishers in the world that you're not even going to show anybody your work to see if it's good or not? Do you really have such delusions of grandeur?
Chances are your manga is never going to be picked up by shonen jump, so showing your ideas through the internet (or even making the series' a webcomic rather than expecting it to get picked up by a publishing company) is a much better use of your time, and will increase the chances of you being able to make a living off of your artwork by an exponential amount.
Also, if you want to be a mangaka, you've gotta practice a lot. I mean, A LOT. Reading a highly romanticized and overrated (and, frankly, largely innacurate) manga about the life of a mangaka isn't going to make you a better artist just because of the supposed "accuracy" and "insiders look" at the industry. You'd do better to actually learn how to tell a story using a series' of images.
Also, don't let "developing the storyline" stop you from drawing it. You're developing the storyline? Okay then; make a different series' and start working on that immediately. You'd be surprised how much making a 4-8 panel webcomic and updating it twice a week will improve your ability, and let you decide if this is really what you wanna do.
Here's an idea for a series: it's an autobiographical series about you being pissed off at everyone in your school because they're all douches and no girl wants to put her mouth around your penis, and every strip you make is a standalone page dealing with your frustrations.