In 785, a 'zo-nagaoka-kyo-shi' (造長岡京使) (one of the extra statutory officers who was in charge of building Nagaoka-kyo), FUJIWARA no Tanetsugu was murdered, and Emperor Kanmu's kotaitei (brother and the first heir to the throne), Imperial Prince Sawara became a suspect and was banished.
しかし、翌785年造長岡京使藤原種継が何者かによって暗殺され、その容疑が桓武天皇の皇太弟早良親王にかけられたため、早良親王が配流される事件が起きる。