Line art pen (water proof) / manga pen with waterproof ink
Paper (for watercolor and smooth surface one if you ink it with Manga pen)
Trace the pencil line use a light box ...
..or draw with a pale pencil in very light touch then ink it.*Don't use an eraser on the paper, it harms the surface!
Lightbox (You can use a glass table instead)
Watercolor ink (Transparent one, not acrylics, Gouache.)
Water brush-pen(Video) or Saishiki Hude彩色筆 (Japanese art brush)
White ink. Waterproof, Brush for white ink.
Fixative. It's keep the white ink steady. (I don't use it)