Kettekino ho, open sleeve seams outer robe (闕腋袍)
The kettekino ho is a garment of chofuku (cloths which the people who came to work at the court on a regular basis wore in the Heian period) in Japan. It refers to a group of terms of Japanese clothes whose sides under the armhole are not stitched, and the front and back areas are seperated. Because the front and back areas are not stitched until the hem, legs are easier to move than in hoeki no ho (robe with a round collar, stitched sides and a ran, worn by the emperor and high-ranking officials).
It is said that Jufuku (everyday court dress in Tang Dynasty) of China, the origin of sokutai (traditional ceremonial court dress) started to be used in the Northern Dynasty (China), and its underarm portions were originally open. This is commonly called "ketteki" in China. What was modified in a Chinese style around Northern Zhou Dynasty is what is called hoeki no ho in Japan. On the other hand, a style of kettekino ho was also popular in and after the Tang Dynasty.
According to the definitions of "the Garment Code" in "Yoro ritsuryo code (code promulgated in the Yoro period)" in the Nara Period, ho (outer robe/vestment) of civil officers' chofuku was called "Koromo" while ho of military officers' chofuku was called "Fusuma." This "Fusuma" is thought to be kettekino ho. Articles left by the deceased of Shoso-in gyobutsu (Shoso-in's Imperial Property) show that the opening of the underarm potions is commonly around 50cm long from the hem. This is different from the Kettekino ho in and after the latter half of Heian Period, which turned into a Japanese style whose underarm portions were all open. It can be imagined that the original purpose for the opening was to meet the convenience of riding on horseback, etc.
In and after the early Heian period, Kugyo worn hoeki no ho even when he concurrently served as military officer. Military officers of shii (Fourth Rank) and goi (Fifth Rank) usually worn hoeki no as sokutai (traditional ceremonial court dress) and worn kettekino ho only on guard of honor in ceremonies or in accompanying Emperor's going out, while military officers of Rokui (Sixth Rank) and lower ranks usually kettekino ho as sokutai. "Zisho Shozokusho (Costumes of the Second in Command)"written by FUJIWARA no Teika, describes the details of the complicated use of the attire by tenjobito (a high-ranking courtier allowed into the Imperial Palace).of shii and goi. In addition, "Jomuchihisho" describes ancient practices in details for the attire of Rokui-Kurodo (kurodo with the Sixth Rank). They also worn ketteki, open sleeve seams, with adjustment of the hem of clothes to the ankle length, when they concurrently work as a military officer, (while civil officers worn hoeki no ho).