First, I'll state the obvious:
THIS IS NOT A GAME.
THIS IS NOT A GAME ENGINE THAT MAKE GAMES.
Now we are clear.
Oh, wait, we aren't.

Now, comes an less-than-obvious fact:
Will it do everything on drawing manga for me?
The answer is NO.

So, if you want something that draws manga for you in 1 click and with a variety of options, STAY AWAY (and hire an artist or something).

Now, with these guys away:
This software is very good for storyboarding and manga-making. But ONLY if you have prior experince on graphic editing and modeling. You don't need to learn to draw, but the more graphical skills you have, the easier you'll be customizing the software, please understand that althrough its build-in resourses are fairly limited, you can freely import your 2D and 3D artworks/models into the program as usable assets, and that, in a way, is customization.

You can look at RPG Maker next door: can you do stuff with the built-in resourses(RTP) using RPG Maker? Sure you can, but the only good works are works that actually has some original creations and creativity put into it. In other words, if you want to use this software effectively, you need to, you know, actually WORK.

I'm finished. I'll leave the rest to you on purchasing the software or not. Remember, a software is only a tool, not a solution, and definitely not for everything.