Taisho Era refers to the era when Takiko Okuda was inside The Universe of the Four Gods, and the summoning of the beast god Genbu along with the tragedic death of the priestess. The Taishou era in itself is named after Emperor Taisho (personal name Yoshihito), father of Emperor Showa aka Hirohito (the one reigning during Suzuno alia Byakko no Miko's adventures) and grandfather of Emperor Heisei aka Akihito (reigning when Miaka and Yui are priestesses of Suzuku and Seiryuu, respectively). It goes between July of 1912 and December of 1926 and it's regarded as the "Taishou Democracy", relatively liberal compared with the conflicted Meiji Restoration and specially with the extreme militarization of the first part of the Showa era, leading to Japan's role in World War Two.