Originally, Shura (Ashura) was included in Tenbu (Deities who reside in a heavenly realm, one of six realms in which the souls of living beings transmigrate from one to another) but after Mahayana Buddhism was established, Shura derived from Tenbu and became Rokudo.
これは当初、修羅（阿修羅）が、天部に含まれていたもので、大乗仏教になってから天部から修羅が派生して六道となった。