In Japan, an insei (院生 insei) is a student at an institution, usually a graduate school. The word may also refer to a student of Go at the Nihon Ki-in (Japanese Go Association) or the Kansai Ki-in (Kansai Go Association) seeking to become a professional player.
Once a year 3-4 Go insei who qualify in a yearly tournament become professional players. The equivalent of Go insei in Korea is "Yeon'gusaeng"(Hangul: 연구생; Hanja: 硏究生; RR: Yeon(-)gusaeng), read "kenkyūsei" in Japanese.
Asian players are required to become a professional before the age of 18 while studying as insei, but foreigners have the chance up to the age of about 30.
To become an insei, a person requires a professional to sponsor them, and an application to the Nihon Ki-in. There is no official way to contact a professional for sponsorship.
While insei, many people live with their professional sponsor, who tutors and supports them. Some insei just visit their professional sponsor several times a week. The professional sponsor acts as a mentor for the insei.