I draw my bat boy character Kuraresu with simple green background and I draw this art in 2007. on this art I use the brush pen on the character outline and it become thick and deep. I think that pen is really easy to use in that time and on this year I notice the pen is Copic Gasenfude the nylon brush pen. on this art I put many colored pencil lines and it make the texture, the outline is deep and it looks clear on many line effect, it's worth to use the brush pen on outlines.

this is the watercolor pencil version[Link].