This study explores the interrelationship between language and the biographical characteristics of the speaker, including gender, age and social status, by examining the interactional functions of two Japanese sentence-final particles ne and na. A major claim in the literature is that although these particles share some similar functions, they differ markedly in terms of gender, age and social status of the speaker: for example, na is used by male speakers only while ne does not have such a restriction. To date, however, little research has systematically examined their differences, and consequently the use of na including its connection with the speaker's gender, age and social status has also been neglected. This study provides a comprehensive analysis of the functions of ne and na by exploring not only their similarities, but also their differences, and sheds light on some aspects of the nature of the identity-language interface. The study will claim that the use of na does not directly indicate the speaker's biographical characteristics. Rather, its special tone of 'camaraderie' is closely linked to sociocultural values on gender and formality in the Japanese language, and consequently its use manifests the particular gender, age and social status of the speaker.