Sennichini prayed to the sun for the early return of Emperor Juntoku from exile on Sado Island for 1,000 consecutive days. Emperor Juntoku, therefore, granted her the name of Sennichini, or 1,000-Day Nun. She was converted to Nichiren's teachings when he was exiled (1271) to Sado by the Kamakura Shogunate. One story goes that she took good care of Nichiren daily for three years during his exile and therefore acquired the name of Sennichini.
Wife of Abutsu-bo, she and her husband were disciples of Priest Nichiren.