司馬穎
Sima Ai became the effective regent, but in order to reduce opposition, he submitted all important matters to Sima Ying, still stationed at Yecheng. As regent, he paid attention to reforming the government, and he saw the importance of formally honoring Emperor Hui while maintaining resemblance to impartial governance. He continued to try to share power with Sima Ying. However, in fall 303, Sima Yong, dissatisfied that his plan did not come to fruition, persuaded Sima Ying to again join him against Sima Ai. While Sima Yong and Sima Ying had overwhelming force, their forces could not score a conclusive victory against Sima Ai. Sima Ai made overtures to try to achieve peace with Sima Ying, but after negotiations, those efforts failed. Sima Yong's forces were about to withdraw in spring 304 when Sima Yue the Prince of Donghai, the grandson of a great-granduncle of Emperor Hui, believing that Sima Ai could not win this war, arrested him and delivered him to Sima Yong's general Zhang Fang (), who executed Sima Ai cruelly by burning him to death. (Before he was executed, Sima Ai was able to write a touching letter of farewell to Emperor Hui.) As Sima Ai cried out in pain, even Zhang's forces were mourning for his fate.