Itou Soukan I retired as Meijin and head of the Itou family in 1691 – the only Meijin in the Edo period to do so, instead of passing on the title upon death. Succeeding him as head of the Itou house was his adopted son, Itou Souin II; and succeeding him as Meijin was his son by blood, Oohashi Soukei V (formerly Itou Sougin, 伊藤宗銀).
Oohashi Soukei V (大橋宗桂, 1636-1713) of the Oohashi main house had presented his 100-problem tsumeshogi collection, the Shougi Tekagami (象戯手鑑) to the shogunate in 1669 when he was promoted to 8-dan.
Having no children of his own, he adopted a son who took the name Oohashi Sougin. Sougin would be involved in one of the shortest yet most intense rivalries in shogi history.