1. Of the judgment of the court of first instance, the part of the claim for ownership transfer registration, including the claim for change at the trial, is as follows.

1. The reasoning for this part of the judgment of the court is the same as that of the reasoning of the judgment of the court of first instance, and thus, this part is cited by the main text of Article 420 of the Civil Procedure Act.

2. Around the time when the Korea Housing and Commercial Bank’s mortgage in the name of the Plaintiff’s claim No. 1 and No. 2 was established, there was a building in an objective and physical aspect due to the completion of the frame, floor, wall, etc. of the apartment newly constructed on that ground. As such, pursuant to Article 20 of the Act on the Ownership and Management of Aggregate Buildings (hereinafter “Act on the Ownership and Management of Aggregate Buildings”), the right to use the site for the land No. 1 and No. 2 owned by the sectional owner of the said building could not

Therefore, even if the Defendant purchased the instant 1 and 2 land from E, which acquired the instant 1 and 2 land through voluntary auction procedure, and completed the registration of ownership transfer, the above transfer registration is null and void against Article 20 of the Aggregate Buildings Act.

Ultimately, the Defendant shall return to the Plaintiff KRW 4,242,00,000, which was paid from the Plaintiff due to the use of the site, to the unjust enrichment, and shall implement the procedure for the registration of ownership transfer with respect to the share corresponding to the share of the instant apartment among the land 1 and 2.

3. Determination

A. Article 20(1) of the Aggregate Buildings Act provides that a sectional owner’s right to use a site shall comply with the disposition of his/her section of exclusive ownership (Article 20(2)), and Article 20(2) of the same Act provides that a sectional owner may not dispose of his/her right to use a site separately from his/her section of exclusive ownership (Article 2 subparag. 6 of the same Act provides that a sectional owner shall not dispose of his/her right to use a site (Article 2(2)). Meanwhile, the Aggregate Buildings Act defines a sectional owner’s right to use a site of a building as a “right to use a site” to own a section of exclusive ownership (Article 2 subparag. 6