He was born the third son of a declining former samurai family in Buzen province, today's Miyako, Fukuoka Prefecture. His pen name was Kosen. He graduated top of his class from the local Toyotsu middle school and went to Tokyo, but at the First Higher Middle School he could not pay his fees and had to leave. He then wrote novels while working as a reporter and teacher in Osaka and Fukuoka.
After being invited by Suematsu Kenchō of his home region to help compile a history of the Mōri family, he became a reporter for Kuroiwa Ruikō's newspaper Yorozu Chōhō. He wrote editorials for social improvement and promoted writing close to spoken language. Among his colleagues were Uchimura Kanzō and Kōtoku Shūsui, with whom he formed a deep, lifelong bond here.
With publisher Kuroiwa Ruikō and colleagues Uchimura Kanzō and Kōtoku Shūsui, he founded a group called the Risōdan aimed at social reform. Through this work he came to sympathize strongly with socialist ideas for ending the suffering of the poor. He would later also come to advocate opposition to war.
As war with Russia approached, the Yorozu Chōhō switched from opposing war to supporting it, so he quit with Uchimura and Kōtoku. With Kōtoku he founded the Heiminsha and published the weekly Heimin Shinbun, starting a movement against war and for socialism, an anti-war stance held against the tide. It was a courageous decision that did not bend his convictions.
During the Russo-Japanese War, he and Kōtoku translated Marx and Engels's Communist Manifesto and published it in the Heimin Shinbun. Although it was translated from the English version, it was the first translation in Japan. Anti-war speech was severely suppressed by the government, and the paper was repeatedly banned from sale.
To spread the socialist movement, he formed the Japan Socialist Party and became a central member. From the previous year he had also taken interest in Esperanto, the proposed universal language, and served as an officer of the Japan Esperanto Association. As a leader of Japan's socialist movement, he worked while keeping in touch with comrades across the country.
He was arrested in the Red Flag Incident, in which young activists raising red flags at a gathering celebrating a comrade's release clashed with police, and was sentenced to two years in prison. Under harsh suppression the movement suffered a heavy blow. Yet this imprisonment would unexpectedly save Sakai's life.
While he was in prison the High Treason Incident occurred and many socialists were arrested, but because he was behind bars Sakai was not caught up in it. After his release, to survive the "winter years" when socialists could not act, he opened the Baibunsha, which took on ghostwriting and translation. It also became a place that gave comrades work and supported their livelihoods.
In the High Treason Incident trial, Kōtoku Shūsui, his friend since the Yorozu Chōhō days, and others were sentenced to death and their lives were taken. Sakai sank into deep grief. Even so, he is said to have visited the bereaved families, showing his care for his comrades. Sakai kept in touch with socialists nationwide and did not let the flame of the movement die.
From the Baibunsha he published the magazine Hechima no Hana, later developing it into the successor magazine Shin Shakai. With writing laced with humor, he kept conveying socialist ideas even under harsh suppression. Through many translations he also worked to introduce Western socialist thought and movements and Western literature to Japan.
As speech gradually grew freer in the Taishō era, he formed the Japan Socialist League, bringing together socialists of various views and labor activists. But the next year its activities were banned by the government. It was an attempt to rebuild the movement after the winter years.
With Yamakawa Hitoshi, Arahata Kanson and others, he joined the first Japanese Communist Party, formed in secret. That same year his translation of the Communist Manifesto was secretly published. But he later sided with Yamakawa's views, left the party and joined the position called the Rōnō faction. Even among comrades, views on how to advance the movement were divided.
Continuing his activities through the Tokyo Proletarian Party he founded, he was elected to the Tokyo city council this year. A socialist who had been imprisoned and endured the winter years now stood in a council chamber, chosen by voters. He kept raising his voice from the political arena to protect the livelihoods of working people.
In Yukuhashi, Fukuoka Prefecture, near his hometown, he opened a farmers' school in the style of a temple school, seeking to bring learning to rural people. But at the end of this year he collapsed with a brain illness and began a life of convalescence. The next year his condition worsened and he was hospitalized, but he left the hospital after about a month.
His condition worsened again, and he died at his home in Kōjimachi, Tokyo. Facing suppression, imprisonment and the death of friends, he never lost his humor and kept guarding the light of the socialist movement throughout his life. His steady support of comrades even in harsh times won him the affection of many.
Uchimura KanzōKōtoku ShūsuiOsugi Sakae
Minakata KumagusuNishida KitarōHonda KōtarōShimamura HōgetsuIzumi KyōkaMinobe TatsukichiSuzuki UmetarōYanagita Kunio
People of the Taishō period ・ People by period
Based on facts found in textbooks and biographies. Uncertain points are marked as such.