1. The plaintiff's appeal is dismissed.

2. The costs of appeal shall be borne by the Plaintiff.

The purport of the claim and appeal is the purport of the appeal.

1. The court's explanation of the facts of recognition and the plaintiff's assertion as to this part is identical to the corresponding part of the judgment of the court of first instance, and thus cite it as it is in accordance with Article 420 of the Civil Procedure

2. Determination

A. In a case where an executive title subject to an objection in a lawsuit of demurrer as to the assertion of subrogation is a final and conclusive judgment, the reason should have arisen after the conclusion of arguments in the relevant lawsuit (see, e.g., Supreme Court Decision 2005Da12728, May 27, 2005). The Plaintiff’s above assertion is obvious that it existed before the date of the conclusion of arguments in the fact-finding proceedings in each of the instant judgments, and thus,

Therefore, the plaintiff's above assertion is without merit to examine further.

B. We examine the existence of the claim for return of unjust enrichment, which is the automatic claim of offset asserted by the Plaintiff regarding the claim for offset.

Article 741 of the Civil Act provides, “A person who gains a benefit from another’s property or services without any legal cause and thereby causes loss to the other person shall return such benefit.”

In the case of the so-called unjust enrichment for which one of the parties has paid a certain amount of benefit according to his/her own will and then claims the return of the benefit on the grounds that there is no legal ground, the burden of proving that there is no legal ground

(See Supreme Court Decision 2017Da37324 Decided January 24, 2018). In light of the Plaintiff’s assertion, D’s KRW 220 million paid to C shall be deemed unjust enrichment. However, the evidence submitted by the Plaintiff alone is insufficient to recognize that there is no legal ground for payment of the above amount, and there is no other evidence to acknowledge this.

Rather, according to the above evidence, especially the related judgments (Evidence No. 2-1, 2, and 3 of the A), the above amount shall be paid “a repayment for a separate contractual obligation with D.”