However, the theory stating that it was adopted in the period of Emperor Tenmu in latter half of 7th century, which was right after the usage of the title by Emperor Gao Zong of Tang mentioned above, has the power, after the mokkan (wood strip), which has the Emperor's handwriting written on, was founded in the Asukaike Ruins in 1998.
しかし、7世紀後半の天武天皇の時代、すなわち前述の唐の高宗皇帝の用例の直後とするのが、1998年の飛鳥池遺跡での天皇の文字を記した木簡発見以後の有力説である。