A fundamental principle in East Asian calligraphy is that the written character must possess ki (life energy or spirit). A technically perfect character without ki is considered dead and Hokusai's sketches have undeniable vitality and ki which can still be felt now.
Kenjin
Inspired by Hokusai
In Hokusai’s work, the term Kenjin (Sages or Wise Men) often refers to the traditional scholars and philosophers of antiquity, most notably the "Seven Sages of the Bamboo Grove" (Chikurin no Shichi Kenjin). These figures were revered for their intellect, poetry, and mastery of the brush.
To convey the heavy folds and draped weight of a sage's sleeves, Hokusai employed thick, swelling strokes that mirror the gyōsho (semi-cursive) and sōsho (cursive) scripts of Japanese calligraphy.