I want to create brushy vector art using look and feel of Japanese calligraphy brush. So I want to ask for help on this, how to do it in inkscape?

I would love to go for brush like this (notice the jittery edges and finishes, also fading in middle on speedy strokes):

Can't be done easily so far. But you know what? Install Krita. It's a free app in all meanings and it has a hairy brush called Sumi-E. It's bitmap graphics, not vector, but you get exactly the kind of brush you want.