Agreement parties -

In other words, a labor agreement is concluded between the labor union itself and the employer or employer's organization as the parties (subjects), while a labor contract is concluded between individual workers and individual employers. Therefore, in the case of a labor agreement, the labor union that concluded the agreement is called the parties to the agreement, and the individual workers who are subject to the agreement are called the parties to the agreement.
[Functions of labor agreements]
When working conditions such as wages and working hours are determined by a labor contract between an individual worker and an employer, the economically weaker worker is in a position where he or she has no choice but to accept the contract conditions unilaterally presented by the stronger employer (however, in cases where minimum standards are stipulated by the Labor Standards Act, etc., certain restrictions are imposed on the employer).

*Some of the terminology used to refer to "parties to the agreement" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…すなわち労働協約は労働組合という団体自体と使用者または使用者団体とを当事者(主体)として締結されるものであり，労働契約は個々の労働者と個々の使用者とを当事者として締結されるものである点において両者は区別される。したがって労働協約の場合，協約を締結した労働組合を協約当事者，その協約の適用を受ける個々の労働者を協約関与者とよぶ。
［労働協約の機能］
　賃金･労働時間等の労働条件が，個々の労働者と使用者との間の労働契約によって決定されるときには，実際上は経済的弱者たる労働者は強者たる使用者が一方的に提示した契約条件をのまざるをえない立場に立たされる(ただし，労働基準法等によって最低基準が法定されている場合には一定の制限が使用者に課せられる)。…

※「協約関与者」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報