1. All appeals filed by the Plaintiff (Counterclaim Defendant) and the Defendant (Counterclaim Plaintiff) are dismissed.

2. The costs of appeal shall be borne respectively by each party.

1. The following facts do not conflict between the parties, or are recognized by Gap evidence Nos. 1 to 5, 8 (including, if any, the number; hereinafter the same shall apply), Eul evidence Nos. 1 to 7, and the result of the appraisal by the first instance appraiser L, as a whole, together with the purport of the entire pleadings.

A. On May 10, 2013, the Plaintiff was awarded a subcontract for reinforced concrete construction works (hereinafter “instant construction works”) from the Defendant among the construction works of the building Adong (hereinafter “instant building”) in Gangnam-gu, Seoul and the construction works of the new building Adong (hereinafter “instant building”) in the same 514-22 new building (hereinafter “instant building”).

B. On the same day, the Plaintiff and the Defendant, in addition to preparing a written contract with respect to the instant building project (hereinafter “the instant primary contract”), prepared a written confirmation on the side of the instant building project with respect to the instant building project as follows (hereinafter “instant written confirmation”).

The construction price of the instant building B: KRW 270,000; Presidential Decree No. 25179, Feb. 28, 2014>

1. The present certification shall have the priority over the standard subcontract agreement of construction in May 10, 2013 by the Plaintiff and the Defendant.

2. It is confirmed that the actual subcontract price that is not the contract price of KRW 1,550,00,000 (excluding value-added tax) that the Plaintiff and the Defendant entered into on May 10, 2013 is KRW 1,350,000 (excluding value-added tax).

3. If the Plaintiff subsequently filed a civil or criminal claim with the Defendant at KRW 1,550,00,000 (excluding value-added tax), the Plaintiff shall compensate the Defendant for the penalty twice the difference between the amount of the standard construction subcontract agreement and the amount of the real construction cost.

2. Determination on the main claim

A. The Plaintiff and the Defendant were first to claim the additional construction cost according to the agreement on the change of the construction cost of the building B in the instant case.