Mugaku Sogen (無学祖元), also known as Bukko Kokushi (1226 – 1286) was a prominent Zen Buddhist monk of the 13th century in Japan, an emigre from Song dynasty China.
He entered the priesthood at Ching-tz'u-ssu temple when he was just 13 years old, and soon afterward, in 1239, he visited Wu-chun Shih-fan, under whom he studied the Zen teachings.
In 1279, he was invited to spread Zen in Japan by Hojo Tokimune, the eighth regent of the Kamakura Shogunate.
In 1282, when Hōjō Tokimune built Engaku-ji temple in Kamakura, he invited Sogen to be the founding priest.
According to legend, Sogen sat quietly on the floor in front of the temple's main Buddha statue.
He built an army with the support of other samurai, regulated internal conditions under his military control, and formed stone bulwarks to keep out the enemy.
Tokimune asked Mugaku Sogen, his Zen master also known as Bukko, for advice.
When Tokimune returned from meditation, Bukko said to him: "Finally there is the greatest event of my life" and asked, "How do you plan to face it?"
One day during their ongoing conversations, Mugaku Shogen took up his pen and wrote one word for Tokimune: Baku-bon-no (莫煩悩).
As a strong follower of the teachings of Zen, Tokimune had planned the construction of the temple to serve as a memorial for the dead from both sides of the conflict.