Ch.2: Age, siblings and seniority
Japanese place a high value on seniority. Most people have heard about the 'senpai' （先輩）and 'kouhai' (後輩）labels put on individuals who are new to a group or company. The 'senpai' (or sempai) is seen as the person having seniority, since he/she has been a member of the work group for longer. He or she is assumed to know the routines and expectations of the job. The sempai is responsible for introducing the kouhai to these things and for overseeing the kouhai's transition into the fold.
Families also have a system of seniority. The 'chounan' (長男）is the eldest son. He is obligated, through Confucian tradition, to take care of his parents in their old age, and he often marries late - his future wife knows she will be living with the in-laws! So this can be a tightrope for Japanese couples to navigate in their courtship and marriage. If there is no chounan - in families with no sons - the eldest daughter, the choujo （長女） - takes on the burden of filial loyalty.
The oldest child often inherits the family business and so this is to their advantage, but the younger siblings have greater freedom to marry whom they please, and to even leave town to pursue their careers or other dreams.