The plaintiffs' claims are dismissed.

The costs of lawsuit shall be borne by the plaintiffs.

1. Basic facts

A. On October 8, 2016, the network D (hereinafter “the deceased”) entered into a sales contract to sell real estate listed in the separate sheet owned by the Defendant and the Deceased (hereinafter “instant real estate”) for KRW 400,000,000 (hereinafter “instant sales contract”) and completed the registration of ownership transfer of the instant real estate (hereinafter “instant transfer registration”) to the Defendant on October 11, 2016.

B. From September 16, 2016, the Deceased died on May 23, 2017, and the Plaintiffs, F, and G jointly inherited the deceased’s property.

[Ground of recognition] Unsatisfy, entry of Gap evidence 1 through 6 (including each number; hereinafter the same shall apply), the purport of the whole pleadings

2. At the time of entering into the instant sales contract, the Deceased did not have the capacity to dispose of his/her property to another person while suffering from dementia in the old age.

Therefore, the sales contract of this case is null and void, and since the registration of transfer of ownership of this case is invalid, the defendant is obligated to cancel the registration of transfer of ownership of this case to the plaintiffs who inherited the deceased's property.

3. Determination

A. At the time of the conclusion of the instant sales contract, whether the deceased had the capacity to perform his/her duties is a mental capacity or intelligence that can reasonably be determined based on his/her meaning or result based on normal perception and towing power. The existence of capacity to perform duties ought to be individually determined in relation to specific legal acts (see, e.g., Supreme Court Decisions 2001Da10113, Oct. 11, 2002; 2008Da58367, Jan. 15, 2009).

A. On April 13, 2012, the Deceased had shown symptoms of Albuses-based dementia after receiving the first diagnosis of the Mazz's disease at H Hospital.