1. The Defendant: 580,218,801 won to the Plaintiffs, and 5% per annum from April 21, 2017 to July 26, 2019, and July 2019.

1. Basic facts

A. On December 22, 2014, joint contractors consisting of the plaintiffs (hereinafter “joint contractors of this case”) were awarded a contract for E Corporation (hereinafter “instant construction”) from the Seoul Local Government Procurement Service for construction cost of KRW 5,154,139,000 (including value-added tax).

B. On October 13, 2016, the Defendant was awarded a subcontract for the instant subcontracted construction work with the construction cost of KRW 1,811,557,000 (including value-added tax) from the instant subcontractor.

C. On November 18, 2016, the Defendant received payment of KRW 1,188,365,200,00 as the subcontract price of this case from the Seoul Local Government Procurement Service, KRW 431,970,00 on December 19, 2016, KRW 208,769,00 on December 28, 2016, KRW 208,769,000 on December 28, 2016, and KRW 194,422,250 on January 25, 2017.

On February 28, 2017, the Defendant suspended the subcontracted construction of this case.

[Reasons for Recognition] Facts without dispute, Gap evidence 1, 2, Eul evidence 1 (including each number; hereinafter the same shall apply) and the purport of the whole pleadings

2. The parties' assertion

A. On February 28, 2017, the Defendant suspended the subcontracted construction of this case, and KRW 1,546,129,760 for the period of the subcontracted construction work, and KRW 1,546,129,760 for the period of the subcontract construction work. The Defendant was obligated to refund the amount of the subcontract construction cost in excess of the period of the contract construction until February 28, 2017, plus KRW 2,126,382,70 for the total construction cost of this case (i.e., KRW 1,188,365,200 from the Seoul Local Government Procurement Service, and KRW 938,017,50 from the instant Joint Supply Agency). Accordingly, the Defendant is obligated to refund the period of the subcontract construction cost to the Plaintiffs, who are members of the instant Joint Supply Agency, the difference between the contract price and the price paid by the Defendant from the Seoul Local Government and the instant Joint Supply Agency, as unjust enrichment.

B. The subcontracted project of this case accounts for 9.035% of the total construction. The Defendant’s subcontracted project of this case accounts for 9.035% of the total construction. As of February 28, 2017, the progress rate of the subcontracted project of this case as of February 28, 20