In 1896, Ryohei Uchida (a skilled martial artist from Fukuoka who had been training at the Kodokan in Tokyo whilst studying Russian) established the first overseas Judo dojo, in Vladivostok.
In the photo, Ryohei is on the extreme left, Jigoro Kano is seated in the middle. Ryohei was a key member of Mitsuru Toyama's Genyosha (Dark Ocean Society) and founded the Kokuryukai (Black Dragon Society) in 1901.
He founded the dojo on the grounds of the Higashi Hongan-ji Mission, across the road from the naval academy. The dojo in Vladivostok was run by six hand-picked men to specifically cater to young Russian military officers. Japan would be at war with Russia by 1904.
With their substantial funding, the Genyōsha and Kokuryūkai were able to establish an extensive infrastructure to aid in their intelligence activities. Along with a training establishment in Sapporo for the training of agents, the Genyōsha would also found a Chinese headquarters (HQ) at Hankou, with a branch in Vladivostok operating under the pretence of a martial arts school. Uchida Ryōhei had established the Genyōsha’s martial arts school in Vladivostok, while Sugiyama acted as director of the Rakuzendō. The school in Sapporo would provide courses in language, including particular dialects, deception and security before an agent's leaving for the Asian mainland. The Kokuryūkai would establish their own “Nationalists’ Training Academy” in Tokyo and the Osaka Foreign Language School. Both provided a curriculum covering all elements related to espionage.
The Rakuzendō, or House of Pleasurable Delights, was connected to the Hankou headquarters and served several purposes. As a mirror image of Stieber’s Green House, the Rakuzendō enticed and then ensnared important personages, but also served as a clearing-house for agents whose reports would be delivered to prostitutes behind closed doors and then forwarded on. The Rakuzendō would also serve as a school of seduction and debauchery, to help agents better entice and acquire the services of those who would be in a position to provide information. The jiu-jitsu school in Vladivostok acted as a base for agents within eastern and central Siberia. Agents could from here be spread along the Trans-Siberian railway. The school was also able to attract Russians of interest with promises of time in the Rakuzendō gratis.
The choice of the temple was no coincidence:
The Genyōsha maintained many agents in Korea at this time, and the society was not lacking in sympathisers, including in the business and religious establishment (the latter predominantly from within the Buddhist Temple, Honganji, which maintained a branch in Busan, Korea).
...While there, the two visited a Major Hanada, already stationed in the city (Vladivostok) under the guise of a Buddhist priest. Hanada, it should be noted, was somewhat derelict in his intelligence duties, not reporting often, and was ordered to return to Japan by Tamura, whereupon he resigned his commission, staying on in Vladivostok as a religious man. Nevertheless, when the war began, the holy man formed an intelligence/guerrilla formation on the orders of Kodama, operating behind enemy lines.
So, as early as 1894 dojo were being used by the most hardcore right-wing groups as intelligence stations.
Items shown in italics are quoted from BLINDED BY THE RISING SUN - JAPANESE MILITARY INTELLIGENCE FROM THE FIRST SINO-JAPANESE WAR TO THE END OF WORLD WAR II by Simon Hall which can be found here, and is highly recommended.