Yu was a type of dress worn on the upper part of the body which was commonly used in Northeast Asia. It was originally used by the Northern race for the need of courtesy as well as protecting cold. It was believed that Yu in Northeast Asia, which was called Kaftan, was came from Scythai lived in North Eurasian land around the Black sea. Scythians were the first-formed horse-riding race in the world and their civilization influenced those of far Asiatic sector along the steppe route. As their power expanded, their costume culture transmitted to the East(China, Korea, Japan). The upper garment, Yu, was characterized by the left-sided collars, narrow sleeves belted at the waist to the length of the hip line and the tight trouser on the lower part, which we commonly called HoBok(胡服) style. 1. Yu in Northeast Asia was originated from the Eurasians, Scythian Culture. Being exchanged, active style costumes were widely used among Chinese, Koreans and Japanese throughout centuries' including $4{\sim}8$ century. 2. Chinese Yu had a style of wide-sleeves and right-sided collars. The traditional costumes of Han race are consisted of wide-sleeved Yu on the upper and long-skirt on the lower part of the body. Before the adoptation of HoBok during reign of King Jo Mooryung in 307. B.C., HoBok style had already found in the remains since the Sang period. There were various names among Yu during the Han period. Seup, Sean Eui, Kye, Kyu were one of the styles and several names were meant for collar and sleeves. During $4{\sim}8$ centuries, clothes of right-sided collar were found, superior to that of left-sided and narrow sleeves were widely used both the royal and the humble. Various styles of decoration were seen in Yu around neck, back and sleeves comparing other nations. 3. Yu, in Korea, was typical style of Northern-bound HoBok. Both men and women had similarity in Yu style, narrow sleeves, left-sided collar, belted at the waist and to the length of hip line. Influenced by Han race, in the $4th{\sim}8th$ centuries, dual system of collar was found. But we cannot see major change in Yu and finally was connected to the present. 4. The original design of the Japanese costumes was not similar to that of Northern nomadic hunting race, which was suitable for horse-riding activities. Owing to the climates along the island, we could see various conditions ranging from the cold and to the warm. Influenced by the climates, pulling over the neck(Pancho style) were major design in Japan. As Korea was advanced earlier than Japan, Korean landed Japanese territory showing clothes. So primitive costumes had changes in style. During the $4th{\sim}8th$ period. The Korean mode was found in Haniwa (which was built to make sacrifices to the dead King) and costumes in Jeong Chang Won. Among the costumes in Jeong Chang Won, we put 3 or more costumes to the category of Yu characterizing elements of Korea and Tang period. From the $4th{\sim}8th$ century, China, Korea, Japan fell into the same cultural category, Scythai. Styles in Yu among three nations, we saw little differences, basically along times. Originated from the West Asia, Yu was transmitted to the far East changing Chinese costumes, Koreans melted it into the traditional elements and then influenced Japan.