Many parts of Tomomasa's life are unknown, but it is considered that at first he called himself Honto as a Buddhist monk in the Shokoku-ji Temple in Kyoto, and in 1458, a person was granted an audience with Seitaishogun (the great, unifying leader) Yoshimasa ASHIKAGA as a representative of Mochitomo, Tomomasa's father, and this person is regarded as Tomomasa.
その生涯には不明な部分も多いが、初めは僧侶として京都の相国寺において本東と名乗り、長禄2年（1458年）に父持朝の名代として征夷大将軍足利義政に拝謁した人物が朝昌の前身にあたると考えられている。