With the arrival of Bp. Sergius in 1908 as Bishop of Kyoto, Fr. Simeon began a long time association with him. Fr. Simeon became Bp. Sergius’ chief assistant when Bp. Sergius succeeded Abp. Nicholas in 1912 following his death. Abp. Sergius, who had been Dean of the St Petersburg Theological Academy, and Fr. Simeon, who alone among the Japanese priests had studied in Russia and knew Russian well, proved to be compatible. Fr. Simeon moved to Tokyo in July 1912, to take up residence at the [[Holy Resurrection Cathedral (Tokyo, Japan)|Kanda Surugadai]] property. In April 1917, Fr. Simeon was raised to the rank of [[protopresbyter]] by the [[Holy Synod]] of Russia.
Also in 1917, Fr. Simeon was named Abp. Sergius’ personal representative to the All Russia Sobor of 1917. He thus became an eyewitness and participant of the events of that year in Moscow. He alone among the Japanese Orthodox clergy was a participant in the discussions during the Sobor and the reinstitution of the [[Patriarch]ate. He also witnessed the happenings in Moscow during the Bolshevik takeover. He was also able to meet again with old friends, former missionary priests, former classmates at the Kiev Academy, and former prisoners of war from the Japanese internment camps, many who had risen to high positions in the Russian church hierarchy. After attending the consecration ceremonies for the new Patriarch [[Tikhon of Moscow|Tikhon]] on [[November 21]], 1917, Fr. Simeon departed for Japan in company with a number of Siberian bishops, finally reaching Tokyo on the last day of the year.
Fr. Simeon, with three other Russian speaking Japanese priests, returned to Siberia in mid-1918 at the behest of the Japanese Government to generate goodwill by providing relief services as part of the so-called ''Siberian Intervention'' by Allied military forces supporting White Russian partisans in Siberia. He returned to Tokyo before Christmas 1918. On returning, Fr. Simeon presented his report on the relief effort to the new Japanese Prime Minister, Kei Hara, Fr. Simeon’s former schoolmate.
Fr. Simeon reposed in the Lord in early 1940 and was buried in the Somei Cemetery in Tokyo.