The judgment below is reversed, and the case is remanded to the Seoul Central District Court.

The grounds of appeal are examined (to the extent of supplement in case of supplemental appellate briefs not timely filed).

1. The obligee's subrogation right under Article 404 of the Civil Code refers to the right of the obligor to exercise the obligee's subrogation right against a third party when it is necessary for the obligee to preserve his claim against the obligor. In this case, it is sufficient if the preservation of the preserved claim is necessary and the due date comes, and it does not require any interference to exercise the subrogation right regardless of the cause of the claim, and it does not require that the obligor's subrogation right can be set up against the third obligor. Thus, in a case where the obligee exercises the obligee's subrogation right, the plaintiff, the obligee, even in a case where the obligee exercises the obligee's subrogation right, must prove the existence of the claim, necessity of preservation, and arrival of the due date, etc., and it is not necessary to prove the fact that the cause of the claim or the fact that the claim is a claim that can be set up against the defendant who is the third obligor. Accordingly, if the obligee's winning judgment becomes final and conclusive by filing a lawsuit against the obligor

(2) On April 11, 200, the Plaintiff purchased 1/2 shares of the instant real estate from K, the former owner of the instant real estate, as indicated by the Plaintiff, and registered the ownership transfer under the name of the networkF, thereby completing the title transfer registration under the name of the networkF. The instant sales contract between the Plaintiff and K is valid, and the registration of title transfer under the name of the deceased and the deceased F between the Plaintiff and K is null and void by the law on the registration of title transfer and the registration of title transfer under the name of the actual owner of the real estate.