A Mangaka is a Japanese comic book illustrator and writer. There are a lot of them but you could be one too.
Most people think that becoming a comic book writer or illustrator is a very hard task, and yes most of it is hard, but the only hard parts are studying art and writing in order to be good at what you and others want to do. All it takes is one great idea to begin someones journey to coming a great or good mangaka.
The only problems someone might have are getting published. Now-a-days it is pretty easy to get published, but you must have an actually good story and the panels must be very well edited and illustrated. Also even if you do get published you must continue to hone your skills and never stop trying to write new stories or draw new panels because the more practiced you are the better chance you will get published again. Some mangakas make their mangas just to meet a deadline, they only care about the money. That is understandable but the fans most of the time can see the lack of thought they put into the manga. Therefor if you become a mangaka you need to decide weather or not you will stick to your own stories and make yourself and the audience happy or if you want to meet a deadline and take a hit from the audience. The decision is yours, because after you get published the hardest task is staying published and getting republished.
Now go out there and follow your dreams. You can do it!