The deity also known as Fudo Myoo in Japan and understood there as a wrathful manifestation of Vairocana Buddha is Acala. His name means “Immovable,” reflecting the steadfast resolve associated with his protection of the Dharma.
Acala is a wrathful deity and dharmapala, or protector of Buddhist teachings. His fierce appearance is traditionally interpreted as compassionate force: flames burn away obstacles and defilements, while his sword cuts through ignorance and his lasso restrains harmful forces. Japanese images of Fudo Myoo commonly show him surrounded by fire and holding these implements.
Acala’s role developed over time. Early esoteric Buddhist sources describe him as a messenger or acolyte of Vairocana. He later became an independently venerated protector and obstacle-remover. In Japanese esoteric Buddhism, the theory of the “three bodies” identifies him as Vairocana’s wrathful embodiment.
The identification is not universal across all Buddhist traditions. Some South Asian, Tibetan, and Nepalese contexts connect Acala with Akshobhya or Manjushri instead. Nevertheless, the question’s Japanese title, Fudo Myoo, supplies the relevant doctrinal setting and makes Acala the canonical answer. He is not the same deity as Ragaraja, Mahakala, or Yamantaka.