Izumo is known as an ancient city in Shimane Prefecture in western Japan. A provincial gazetteer titled the "Izumo Fudoki" (『出雲風土記』, 733) is the most important one and the only one that is complete, in which a mute son in the age of the gods is stated.
His name was Adisikitakahikone no Mikoto (阿遅須伎高日子命), the son of a god Ohokamiohoanamoti no Mikoto (大神太穴持命) who is said to be one of 50 gods enshrined in Izumo.
According to the "Izumo Fudoki", the son had grown up with the full mustache. However, he was not able to speak, only crying through all day and night like a baby.
Father tried to comfort him by taking him aboard a boat, which sailed around Yasoshima Island, but the boy never stop crying. Father even constructed a tall house, which Son climbed up and down many times with the ladder. Yet no words spoken from his mouth.
Worried Father god prayed to the dream. Soon a child appeared in the dream and emitted a word "Mitsu". Father inquired, "What is it?"
He was told to visit Mitsu in Izumo where a spring flowed. He purified himself with the water, and the mute boy was able to speak finally. A folk tale in Izumo says that a pregnant woman must not eat rice because of the fear that a mute baby boy would be born.
Son, Adisikitakahikone no Mikoto later played an important role in the ancient history and he is currently worshiped as a god of agriculture, god of thunder, and god of real estate business, too.