Kawahigashi Hekigotō abandoned the 5-7-5 pattern and called his verse tanshi.
Hekigotō was a major modernizer of haiku and a disciple of Masaoka Shiki. After Shiki’s death, he pushed experimentation further by rejecting the fixed 17-on structure traditionally represented in English as 5-7-5. He favored free verse based on the poet’s immediate impression rather than an imposed syllabic pattern.
The term tanshi can be translated broadly as “short poem.” Hekigotō used it to distinguish his freer compositions from conventional haiku. He generally retained the seasonal word, or kigo, even while challenging the metrical structure; some of his followers later abandoned that feature as well.
This reform movement helped split modern Japanese haiku into competing directions. Takahama Kyoshi defended more traditional formal and seasonal conventions, while Hekigotō and writers influenced by him pursued freer expression. Renku is linked verse, waka is a different traditional poetic form, and haibun is a prose-and-poetry genre, so none of those names fits Hekigotō’s label.