In Japan, Fudo Myoo (Acala) is widely popular and venerated, including in the context of Esoteric Buddhism, which includes practices that utilize mantras to attain enlightenment. One of the mantra versions chanted in veneration of Fudo Myoo is: "No-maku Samanda Bazara (da) Senda Makaroshada Sowataya (um) Tarata Kanman."
It said that Kukai brought Fudo Myoo (Acala) into Japan. Kukai is posthumously known as 弘法大師 (Kobo Daishi) and founded the Shingon Buddhism in Japan following his returning from his Kentoshi mission in China (or to be more precise, the Tang Dynasty).
Although the Fudo Myoo looks as though it is a god of battle or war, it actually is very merciful and he provides salvation to people who suffer from polluting thoughts such as greed, hatred and delusion, all of which result in suffering. It is thought that the deity makes use of his lariat and sword to eliminate such polluting thoughts, thereby helping us attain enlightenment.