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

The Defendants shall jointly and severally serve as the Plaintiff KRW 63,650,000 and KRW 40,000.

1. The reasons for the acceptance of the judgment of the court of first instance are as stated in the reasoning of the judgment of the court of first instance, except for the deletion of four parallels and five parallels in the nine pages of the judgment of the court of first instance and addition of the following additional judgments, and they are quoted as they are in accordance with the main sentence of Article 420 of

2. Additional determination

A. As seen earlier, the Plaintiff has a claim for the construction cost of KRW 70,000,000 against the Defendants, and the Defendants have the damage claim against the Plaintiff in lieu of the defect repair of KRW 30,000,000.

However, through the Plaintiff’s application for modification of the purport of the claim and the cause of the claim on September 4, 2020, the Plaintiff expressed to the Defendants a set-off of the Plaintiff’s claim for construction price against the Defendants within the extent equal to that of the Defendant’s damage claim in lieu of the defect repair. The fact that the above application for modification of the purport of the claim and the cause of the claim was served to Defendant B on September 10, 2020, and to Defendant C on September 16, 202

In addition, the damage claim in lieu of the defect repair of the Defendants, a passive claim, was deemed to have arrived on August 2, 2017, which appears to have been completed by the construction of the instant case as seen earlier. Since the Plaintiff’s claim for construction payment, an automatic claim, also became due on August 2, 2017, it is reasonable to view that each of the above claims was set-off on August 2, 2017.

Therefore, the above automatic claim and the passive claim are extinguished within the scope on an equal basis on the set-off date, and eventually, the plaintiff's claim for construction payment against the defendants remains at KRW 40,000 (=70,000,000 - KRW 30,000).

The plaintiff's offset defense is reasonable, and the defendants are obliged to pay to the plaintiff the balance of the construction price of KRW 40,000,000 and delay damages.

B. The Plaintiff’s assertion of the Defendants as to the Defendant’s conjunctive set-off defense against the Defendant’s value-added tax is against the Defendants without any justifiable ground.