It is a pen that is softly applied and blurred. Once the pen is laid, blur it more widely.
If you turn off the border of watercolor, the shallow edges will disappear and you will be able to paint 100% smooth.
柔らかく塗ってぼかすペンです。ペンを寝かせたらもっと広くぼかせます。
水彩境界をオフにすれば、浅い縁がなくなって100%すべすべな塗りができます。