This pen was made when I was tinkering with the pen I wanted to use for line drawings. 自分が線画などで使いたいペンを求めていじってたらできたペンです。
Since mix ground color (color mixing) is added, it is easy to draw roughly, such as changing the intensity when drawing on top of each other. (personally)
下地混色(色混ぜ)を入れてるので描き重ねると濃さが変わったりなどしてざくざく描きやすいです。(個人的に)