Complex sentence: In Shinto tradition it was said that the eight million gods of Japan left their shrines to congregate annually at Izumo Taisha, and in Izumo province this month was therefore known as, "the month when the gods are present".
Split into simpler sentences: In Shinto tradition it was said that the eight million gods of Japan left their shrines and congregated annually at Izumo Taisha. There the month was known as, "the month when the gods are present".