The judgment of the first instance is revoked, and the lawsuit of this case is dismissed.

The plaintiff's total costs of litigation.

1. Article 252(1) of the Civil Procedure Act provides, “The parties to a judgment may file a lawsuit claiming to change the amount of periodic payments to be paid in the future, when special circumstances arise that greatly undermine equity between the parties, as the circumstances forming the basis for computing the amount were significantly changed following a final judgment ordering the payment of periodic payments.”

The purpose of this lawsuit is to exceptionally exclude res judicata of a final and conclusive judgment on the grounds of significant change in circumstances that occurred after the final and conclusive judgment of periodical payments became final and conclusive. As such, it is reasonable to deem that only the parties to the final and conclusive judgment or a third party whose res judicata effect on the final and conclusive judgment pursuant to Article 218(1) of the Civil Procedure Act can bring an action for change in the final and conclusive judgment.

Meanwhile, in a case where a land owner filed a lawsuit seeking a return of unjust enrichment equivalent to the rent amount against an illegal occupant of the land based on the ownership and the judgment that the illegal occupant returned unjust enrichment equivalent to the rent amount each month until the delivery of the land in possession becomes final, the subject matter of such lawsuit is the right to claim a return of unjust enrichment, which is the obligatory claim, and thus, the person who acquired the ownership of the land after the closing of argument in the lawsuit cannot be deemed to fall under the successor subsequent to the closure of argument in which the res judicata effect of

(See Supreme Court Decision 92Da25151, Feb. 12, 1993). Therefore, with respect to a person who acquires the ownership of the land after the closing of argument in a lawsuit seeking return of unjust enrichment brought by the former owner of the land, the res judicata effect of a final and conclusive judgment ordering a regular prohibition order issued in the above lawsuit does not extend to the person who acquired the ownership of the land. Therefore, the new owner of the land does not bring