Manga effect. One side glass coating? Link to 3D model: https://sketchfab.com/models/44e355c0b8d94f7a8a59e5034d3bc3d7

This a a fantastic artwork created by a Japanese 3D artist Atsushi Tamaki.

I was amazed by the manga-outline effect on the character and have been trying to work out how it can be done, but no luck so far. What I can tell is that it seems like the character is coated by a one-side transparent coating(transparent if view from out side, pure black if view from in side).

Looking for some advice. Thank you!
Expanding on the first point of John's answer.


  For realtime or viewport effects like this the general idea is to duplicate the mesh, then change that mesh to complete black then slightly upscale it so it covers your base mesh, as well as flipping all the normals on the black mesh and turning on 'Backface Culling' in the viewport settings.



&#8679; ShiftD to duplicate.
Enter Edit Mode &#8633; Tab, select all A, flip normals &#9096; CtrlF > Flip Normals.
Fatten the mesh slightly, &#9095; AltS.
Exit edit mode and assign a new black Material.
Turning off double sided faces in Blender: Go to the Shading Panel and check Backface Culling.