A linguist from Morioka, Iwate, who became lifelong friends with Ishikawa Takuboku at Morioka Middle School — and Takuboku's single greatest supporter. He believed in Takuboku's genius more than anyone, pawning his household possessions every time his friend came asking for money. His wife called Takuboku "a complete thief," yet Kindaichi never stopped helping him. At Tokyo Imperial University he devoted himself to Ainu language research, spending his life recording and preserving a language on the brink of extinction — becoming Japan's foremost Ainu linguistics scholar. In his later years he helped compile Sanseido's "Meikai Kokugo Jiten" (National Language Dictionary), beloved by generations. Even after Takuboku's death, he worked tirelessly to spread his friend's literary legacy. His grandson Kindaichi Hideho is also a linguist. He died at 89.

Genuinely warm-hearted, with an extraordinary capacity for devoted support of talented people. The sheer magnanimity it took to remain loyal to a friend like Takuboku — a champion borrower — without a word of complaint is remarkable. As a scholar, he was a rigorous empiricist who threw himself into fieldwork to document and preserve the dying Ainu language.

He left an enduring mark on the history of linguistics as a pioneer who laid the foundations of Ainu language study. His "Meikai Kokugo Jiten" remains beloved by Japanese readers as "Kindaichi's dictionary." He is also the unsung hero of modern literary history: without his devoted support, Takuboku's "A Handful of Sand" might never have been published.