Senpai and kōhai 前辈
(重定向自Sempai)
In Japan, senpai(先輩) is an upperclassman, someone of a higher age, or senior and kōhai(後輩) is a protégé or junior. The mentor system is found at all levels of education, and in sports clubs, businesses, and informal or social organizations. The relationship is an essential element of Japanese seniority-based status relationships, similar to the way that family and other relationships are decided based on age, in which even twins may be divided into elder and younger siblings.