How do I draw like the image attached to this post?

[senjaez49486447]

What I want to achieve is to draw shades like the image shown above.
I know how to put gradation and all that.

The only wonder is how I could have colors within shape of the face, even though the shape that I draw with pen tool is extending outside of the face (just like how blue lines are extended outside of the face, but gradation only stays within the face).

How could I achieve this?

[Monika Gause]

That is a clipping mask.

[jane-e]

And the shading is done with a mesh object. The basics are here; you can find other tutorials as well.

https://helpx.adobe.com/illustrator/using/meshes.html

The third thing you will need, of course, is an understanding of shading and some artistic ability, to create that kind of artwork.

[Monika Gause]

There's no mesh in that sample. It's just a gradient.

[Ton Frederiks]

Merging no fill / no stroke paths with a Live Paint object will allow you to add shading to a drawing.

[Ray Yorkshire · Accepted solution]

It's from this video?

hardly a tutorial, more a speed  demonstration..

Drawing and Coloring Tutorial for Adobe Illustrator - YouTube

Probably better off using Clip Studio Paint for colouring like that, as its more sophisticated,

even if you import the line work from illustrator,