The judgment below

The part against the defendant is reversed, and the judgment of the first instance on this part is revoked, and this part is revoked.

Judgment ex officio is made.

1. As to the Defendant’s appeal

A. In principle, res judicata of a final and conclusive judgment is recognized only as included in the text. However, even if it is included in the reasons, res judicata extends to the amount of automatic claims asserted as a offset only in the amount set-off (Article 216 of the Civil Procedure Act). Moreover, in a case where the existence of rights or legal relations disputed in a lawsuit and a final and conclusive judgment is rendered in a prior suit between the same parties, the parties cannot make any arguments that conflict with this, and the court cannot make any judgment that conflict with this, and the above existence of a final and conclusive judgment should not be determined ex officio by the court, even if the parties did not assert the existence of a final and conclusive judgment by the time the arguments are closed at the trial court, and even if the parties did not assert the existence

(see, e.g., Supreme Court Decisions 89Nu1308, Oct. 10, 1989; 2017Da231232, Feb. 13, 2018). Meanwhile, given that a final and conclusive favorable judgment has res judicata effect on a final and conclusive favorable judgment, where a party who received the final and conclusive judgment in favor files a lawsuit against the other party to the previous suit for the same claim as that of the final and conclusive judgment in favor of the former suit, barring any special circumstance, the subsequent suit is unlawful as there is no benefit

B. (See, e.g., Supreme Court Decisions 87Meu1761, Nov. 10, 1987; 2005Da74764, Apr. 14, 2006).

The judgment below

According to the reasoning and the record, ① in the lawsuit claiming the purchase price of goods (Seoul High Court 2016Na2086785, hereinafter “instant prior suit”) brought by the Defendant against the Plaintiff, the Defendant’s claim for the purchase price of the goods of this case equivalent to KRW 214,739,870 against the Plaintiff was recognized, and ② in the prior suit of this case, the Plaintiff has the claim for the damages of KRW 194,03,839 against the Defendant on the ground of the same cause of the claim.