Wow!!
Help me understand: this was drawn entirely without paper and pencil? "digital painting and graphics (pen, pen, marker)" - "using the Paint Tool SAI. Wacom Intuos Pen Small tablet. The graphic tablet is on the working computer desk" - eh. I still don't get it. My husband will have to show me the ropes. He draws horses like this, by hand. Portraits of pets and people. Landscapes.
Anyone who thinks drawing via a computer is "cheating" is crazy. This looks totally outside my skill set. I'm in awe of your talent, and this horse!!