He was the first king to rule Baekje from its new capital in Ungjin, present-day Gongju, after the Han River valley was lost to Goguryeo.
Prior to 475, Munju served as chief minister (Sang-jwa'pyeong, 上佐平) under his father, Gaero.
According to the Samguk sagi, he returned with 10,000 Silla warriors but was too late to prevent the fall of the capital.
He sought to refortify Baekje's remaining defenses and strengthen the country's position against Goguryeo.
In the midst of this instability, the chief general and Minister of Defense, Hae Gu, took control of the military and killed Munju's brother Buyeo Gonji in 477.