As you know, Naesi of the Kory? dynasty consisted of Jokwannaesi(朝官內侍), S?rinaesi(胥吏內侍), and Sanjiknaesi(散職內侍). Among them, the most important was Jokwannaesi. Guy civil officials could be Jokwannaesi primarily, but from the period of military ruler, military officials began to step in. And in the early years of King Chungry?l(忠烈王), Naeryo(內僚) that included bastards and eunuches were allowed to have such qualification. Naeryo distinguished themselves in a series of political struggles that were happened in the late period of military rule. In reward for that, the king allowed them to became Jokwannaesi, and they made their way to becoming Jokwannaesi with military positions.
But by the time of King Chungry?l, the core members of Naesi were still people from civil officials. And after King Chungs?n(忠宣王), the Naesi came from military officials. That was because all Naesi, including Jokwannaesi, were considered as supernumerary of government officials by King Chungs?n's unique reign named J?njij?ngchi(傳旨政治). As a result, all the groups of Naesi came to lose the king's trust, it made the civil officials of ability mind being Naesi. But Naeryo from bastard children desired to be Naesi, so they filled the vacancies naturally. According to such a change, Jokwannaesi with military positions, of which military officials and Naeryo took charge, became the core members of Naesi. This means that Naesi's original characteristic of the Kory? dynasty changed.
After that, during the period of King Gongmin(恭愍王) there was another big change in the Naesi system of Kory? dynasty. Jokwannaesi with military positions of which military officials and Naeryo took charge disappeared, instead S?ngjungkwan(成衆官) Naesi who were from S?ri(胥吏) became the core members of Naesi. The Setting up of Chungyongwee(忠勇衛) and consolidation of the eunuch system became its moment. With the organization of Chungyongwee, king's bodyguards, Naesi from military officials, were assigned to them, and Naesi from Naeryo came back to the eunuch of Chamjik(參職) with tile arrangement of eunuch system So the Naesi changed into the group in which S?ri played a leading role. And at that time, people who were from shabby families and tried to escape their military duties rushed to the places that Naesi with military positions had left. In the end, the Naesi changed into SOngjW1gkwan and such continued to the early Chos?n(朝鮮) dynasty.