Thousands of years ago, Tsukuyomi realized that Earth was an impure, blood-stained world, which was stealing life from all living beings. So, this sage left Earth and took with him his most trusted relatives, including Eirin Yagokoro, his elder who he relied on the most, and founded the Lunar Capital. The Moon lacked the impurities of Earth and those who took up residence there forsook any lifespan, meaning they were neither alive or dead, but because they are not truly immortal.