The Nagayao no Hen (the Conspiracy of Nagayao) in 729, which led to his suicide, is believed to have been a conspiracy organized by the four brothers in order to slander and expel Nagayao, who had been opposed to their attempt to make Komyoshi, their half-sister and the Emperor's wife, the first Empress chosen from outside the Imperial Family.
729年に長屋王の変が起こり長屋王は自害するが、これは四兄弟が自分達の異母妹で天皇の妃である光明子を史上初の皇族以外出自の皇后に立てるため、それに反対する長屋王を讒言により陥れた陰謀事件であったといわれている。