On March 23, 870 during the era of Prince Koretada, he was demoted from nobility to subject with his brother, Prince Koresada, and his paternal brothers, and referred to himself as MINAMOTO no Koretada.
是忠王時代の貞観(日本)12年2月14日(旧暦)（870年3月19日）に弟の是貞王や異母兄弟とともに臣籍降下して源是忠（みなもとのこれただ）と名乗った。