It is one of the five male gods born from the Iotsu Misumaru no tama necklace of the Yasaka no magatama Bead of Amaterasu Omikami (the Sun Goddess), when Amaterasu and Susano took their oath.
アマテラスとスサノオの誓約の際に、天照大神の八尺勾玉の五百箇の御統の珠から生まれた五柱の男神のうちの一柱である。