Takuboku Ishikawa (石川 啄木 February 20, 1886 – April 13, 1912) was a Japanese poet. He died of tuberculosis. Well-known as both a tanka and "modern-style" (新体詩 shintaishi?) or "free-style" (自由詩 jiyūshi?) poet, he began as a member of the Myōjō group of naturalist poets but later joined the "socialistic" group of Japanese poets and renounced naturalism.
Read this in parallel with Shiki's haiku collection, but Ishikawa's tanka win the day by a huge margin for me. He is a master of portraying these tiniest/subtlest moments from everyday life that are full of wabi-sabi, leaving you a bit sad, a bit empty, and a bit more aware of life around you. The longer form of tanka compared to haiku—bigger canvas—might limit/define what each form can do, but I very much appreciate what Ishikawa's tanka do over Shiki's haiku informed by the literary naturalism of 18th century France. Definitely a fan.