The reason for Narichika's conspiracy is explained in the "Tale of Heike," as follows: When Narichika expressed the desire to take the post from which FUJIWARA no Moronaga had resigned, the two brothers, TAIRA no Shigemori and Munemori, were appointed Generals of the right and left, for which Narichika held a grudge.
成親が陰謀を企てた理由として、『平家物語』は近衛府の藤原師長の辞職した後任を所望したところ、平重盛と平宗盛の兄弟が左右大将に任命されたことを恨みとしたとする。