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

The Defendant-Counterclaim Plaintiff (Counterclaim Defendant) is 12,668,793 won and 12,668,793.

A principal lawsuit and a counterclaim shall be deemed simultaneously.

1. The court's explanation on this part of the basic facts is identical to the corresponding part of the reasoning of the judgment of the court of first instance, and thus, citing it as it is by the main text of Article 420 of the Civil Procedure Act.

2. The parties' assertion and judgment

A. The plaintiff's assertion and judgment (1) The defendant asserted that the plaintiff paid 122,286,226 won to the plaintiff out of the original and additional construction costs of this case (i.e., the changed original construction cost of KRW 132,00,000 - the payment of KRW 55,000,000 - the direct payment of KRW 79,464,000, the additional construction cost of KRW 124,750,246) and damages for delay shall be paid to the plaintiff.

(2) In full view of the purport of the argument as a result of the appraisal by the appraiser E of the first instance trial, the Plaintiff performed additional construction works such as ancillary facilities and warehouse construction at the Defendant’s request. The appraiser E of the first instance trial assessed the instant additional construction cost as KRW 108,41,615 by applying the bid price rate of KRW 87.75% when a negotiated contract is concluded, but the instant additional construction cost must be included in the instant additional construction cost (However, as seen earlier, the Defendant’s payment on behalf of the Defendant was deducted from the Plaintiff’s bid price) and the additional construction cost should be deducted from the bid price rate of KRW 87.75% at the time of a negotiated contract, and there is no ground to apply the bid price rate of KRW 100 to the additional construction cost.

Therefore, barring any special circumstance, the Defendant should pay to the Plaintiff the amount of KRW 121,082,00 that is unpaid for the instant original and additional construction works (i.e., the original construction cost of KRW 132,00,000 - the amount of KRW 55,00,000 - the amount of direct payment of KRW 79,464,00,00 for additional construction works, 123,546,00 for additional construction works).

B. The defendant's assertion and judgment (1) The defendant's assertion made a substitute payment on June 26, 2017 as a joint and several surety in accordance with the court's decision to recommend reconciliation in respect of F Co., Ltd. to be repaid by the plaintiff.