Kegare is the Shinto idea of ritual impurity or defilement. It is best understood not as moral guilt but as a state in which life-force is diminished or withered, a dulling of the brightness and vitality that the kami love and that ordinary life should have. Its typical sources are death, blood, disease and decay: the things that oppose freshness and life.
Because kegare is a condition rather than a crime, it can be contracted without any wrongdoing at all, by proximity to death, for instance, and it calls not for forgiveness but for removal. That removal is purification, harae, and the two ideas belong together: much of Shinto practice is organized around the movement from pollution to cleanness, so that a person or place is made fit once more to approach the kami. The pattern is set in myth by the god Izanagi, who is defiled by his journey to the land of the dead, Yomi, and cleanses himself by washing in a river on his return, the primordial act of purification from which, the Kojiki says, further kami are born.