1. The judgment of the court of first instance is modified as follows.

The defendant shall pay to the plaintiff KRW 280,836,639 as well as to the plaintiff on August 2017.

1. The reasons why the court states this part of the basic facts are the same as that of the judgment of the court of first instance, and therefore, they are cited in accordance with the main sentence of Article 420 of the Civil Procedure Act.

2. Determination as to the cause of action

A. The Plaintiff’s assertion 1) The Plaintiff is obligated to pay the remainder of KRW 789,00,000 among the construction cost of this case (i.e., the construction cost of this case 989,00,000,000 - down payment 200,000) and the additional construction cost of KRW 44,330,00 for the portion not included in the contract of this case, 833,330,000 for the additional construction cost of KRW 425,788,168, 400 for the person who was paid by the Plaintiff and the Defendant, and the delay damages therefrom. (ii) Even if there was no agreement between the Plaintiff and the Defendant on the additional construction cost, the Defendant is obligated to return it to the Plaintiff as unjust enrichment, and thus, the Defendant is obligated to pay the Plaintiff the said additional construction cost of KRW 44,330,00,00 for the additional construction cost of this case.

B. 1) Determination 1) The construction work in this case’s determination of the claim for the remainder of the construction cost of this case was completed on December 30, 2016, and the Defendant agreed to pay the remainder within one month after the completion of the building of this case as seen earlier. As such, the Defendant is obligated to pay the Plaintiff additional construction cost of KRW 789,00,000 and delay damages therefrom. 2) In the event that the construction contract of this case’s legal doctrine is the total amount of construction cost and the total amount of construction cost determined for the entire construction work, even if the contractor entered into the construction work in accordance with the design drawings and entered into a contract for the total amount of the construction cost, the contractor cannot be deemed as the additional construction work and the contractor cannot be deemed as having made unjust enrichment (see Supreme Court Decision 2010Da17635, Jul. 8, 2010).