1. The Plaintiff (Counterclaim Defendant) paid KRW 30,022,118 to the Defendant (Counterclaim Plaintiff) and its related expenses from June 13, 2017 to July 21, 2017.

A principal lawsuit and a counterclaim shall be deemed simultaneously.

1. Basic facts

A. On October 11, 2013, the Plaintiff entered into a contract with the Defendants under which the Defendants entered into a contract for the construction of the Yeongdeungpo-gu Seoul Metropolitan Government Officetel (hereinafter “instant construction”) with the construction period of KRW 3,630,000 (including value-added tax; hereinafter the same shall apply) from October 1, 2013 to October 31, 2014.

B. On October 28, 2013, the Plaintiff commenced construction of the instant construction and obtained approval for use on August 22, 2014.

C. The Defendants paid the Plaintiff KRW 3,350,000,000 in total with the construction cost of the instant case, and rejected the payment of KRW 280,000,000.

On the other hand, when performing the instant construction, the Plaintiff did not perform or modified construction of the part to be constructed in accordance with the design drawing, resulting in a defect. This resulted in a defect in the function, safety, or aesthetic view of the instant building.

E. On December 5, 2014, December 26, 2014, the Plaintiff sent to the Defendants a written request for approval of construction cost of KRW 280,000,000 and additional construction cost of KRW 125,40,000, and a written request for approval of construction cost by content-certified mail.

[Ground of recognition] Facts without dispute, Gap evidence 1 through 3, Gap evidence 7, Gap evidence 14 through 18 (including each number; hereinafter the same shall apply), Eul evidence 1 to 5, the result of the appraisal commission to appraiser E by this court, the purport of the whole pleadings

2. The parties' assertion

A. Although the Plaintiff completed the instant construction work, the Defendants did not pay KRW 280,000,000 to the Plaintiff out of the contract price. (2) Upon the request of the Defendants, the Plaintiff included the items of “1. Additional Construction” in the attached Form “1. Additional Construction” from November 1, 2013 to September 30, 2014.