Then, in the case law holding that the person who asserts his or her own claim to performance is the plaintiff and the person alleged to be obliged under the claim is the defendant, the meaning of "the plaintiff's claim itself" is as follows: given that the required entries in the complaint are the indication of the parties, the purport of the claim and the grounds of the claim, "the plaintiff's claim itself" means identifying the parties with a focus on these three required entries.

In Chapter 2 (Parties), the Civil Procedure Act has Section 1 on capacity to be a party and litigation capacity. Article 51 of the Civil Procedure Act, as the principle on capacity to be a party, litigation capacity and the like, provides that capacity to be a party, litigation capacity, legal representation of persons without litigation capacity, and the grant of authority necessary for litigation acts are governed by the Civil Act and other statutes unless this Act provides otherwise. Article 52, on the capacity to be a party of unincorporated associations and the like, provides that an unincorporated association or foundation may be a party in its own name if it has a representative or administrator. Article 53, on appointed parties, provides in paragraph (1) that where several persons with common interests do not fall under Article 52, they may appoint, or change, one or more persons from among them to be a party for all of them, and in paragraph (2) that where the parties are changed under paragraph (1) after the suit is pending before the court, the former parties are deemed to have withdrawn from the suit as a matter of course.

Since the determination of the parties first becomes an issue from the service of the complaint on the parties, before serving the parties the court must judge whether the indication of the parties in the civil suit filed is made accurately as the holders of substantive rights or legal relationships, or as a third party conducting litigation on another's behalf. To do this, it is considered to be linked first to the question of to what level the required entries in a civil complaint must be stated in order to conform to the spirit of the Civil Procedure Act that requires them.

When determining the parties, the principle is that the relationship between the holder of the substantive right or legal relationship and a third party is indicated. However, such a statement is not necessarily required unconditionally. Accordingly, a method of handling is needed where the relationship between the holder of the substantive right or legal relationship and a third party does not appear. In the indication of the parties in a civil suit so filed, whether the holder of the substantive right or legal relationship filed the suit, or whether a third party filed it in the position of a person conducting litigation on another's behalf, can be judged from the purport and grounds of the claim. Therefore, where, by such a method, it is unclear whether the person indicated as a party is the holder of the substantive right or legal relationship, one may or may not take the view that such a relationship must be indicated in cases of third-party litigation on another's behalf. If one takes the view that it must be indicated, then, by interpretation, where it is not indicated, the person stated as a party should be interpreted as a party to the suit as the person with the power to manage and dispose of the substantive right or legal relationship. It cannot be legally presumed that every suit in which the complaint does not indicate whether it is third-party litigation is filed by the person with the power to manage and dispose of the substantive right or legal relationship.

Determination of the parties and standing to be a party are first-step issues that almost always appear in case-type questions on civil procedure. Organizing together the method of determining the parties by reading the complaint as a whole under the modified indication theory, the difference between correcting the indication of a party and substituting the defendant, and examples of third-party litigation such as creditor's subrogation suits and collection suits gives you the ability to start the first paragraph of an answer accurately. Studying them bundled with provisions that often appear in practice, such as appointed parties and the capacity to be a party of unincorporated associations, lets you organize the whole unit on parties at once.