Izanami-no-Mikoto is the primordial Shinto earth-mother goddess and sister/wife/counterpart to Izanagi-no-Mikoto. She helped stir the oceans on the Bridge of the Heavens, and settled down with Izanagi on Earth on their island Onogoro. On their first marriage ceremony she made the mistake of speaking to Izanagi first, so the ritual had to be repeated. After the second ceremony she gave birth to various deities.
But then she gave birth to Hi-no-Kagutsuchi the Deity of Fire, and died from the severe burns of the flames. When she perished, she went to Yomi, the Land of the Dead. Izanami ate from the furnace of Hell, and went to petition the deities of the Netherworld to let her go. She made her husband promise not to look at her, but Izanagi did anyway and was greeted by the sight of a rotting corpse with the Eight Thunders protruding from her body.
Ashamed by Izanagi's indiscretion, she sent the Yomotsu-Shikomes, the Thunders and Yomotsu-Ikusas after him. Izanagi sealed the entrance to Yomi with a boulder, and Izanami cried, "Why did you do such a thing to me?! You betrayed me!! Remove this boulder this instant or I'll kill 1000 of your subjects everyday!" Izanagi countered, "For every 1000 you kill, 1500 shall be born in their place!" and thus their marriage was over. She became the Yomotsugami, the Goddess of the Land of the Dead.