1. All appeals filed by the plaintiffs are dismissed.

2. The costs of appeal are assessed against the Plaintiffs.

The purport of the claim and appeal is the purport of the appeal.

1. The reasons why the court should explain this part of the basic facts are cited by the main text of Article 420 of the Civil Procedure Act, because it is the same as the corresponding part of the reasoning of the judgment of the court of first instance.

2. The plaintiffs' assertion

A. The instant provision is deemed null and void as it violates Articles 6(1), 6(2)1, and 11 subparag. 1 of the Regulation of Standardized Contracts Act (hereinafter “Standard Contract Regulation Act”) and is thus null and void as it violates Article 19 of the Act on Contracts to Which the State is a Party (hereinafter “State Contract Act”) and Article 64(1)2 and (7) of the Enforcement Decree of the same Act, and is null and void as it violates Article 3(3) of the General Conditions of the Contracts to Which the State is a Party, which provides for the adjustment of contract amount due to price fluctuation, etc. (hereinafter “State Contract Act”).

B. Even if the instant provision is valid, ① the Defendant did not explain the instant provision, which is an important content of the terms and conditions at the time of entering into the instant contract, pursuant to Article 3(4) of the Act on the Regulation of Terms and Conditions, the said provision cannot be asserted as the content of the contract. ② Since the instant provision suffered exchange loss, due to abnormal exchange rate increase in the global financial crisis following the conclusion of the instant contract, the amount of the contract should be adjusted according to the principle of good faith, inasmuch as it was incurred by the Plaintiffs

C. Nevertheless, by the Defendant’s refusal to adjust the contract amount due to the exchange rate fluctuation due to the old room, the Plaintiffs additionally bear KRW 13,130,013,00 due to the exchange rate fluctuation, while the Defendant gains profits equivalent to the same amount without any legal grounds, and thus, the Defendant seeks a return of the amount of unjust enrichment, such as the written claim, as stated in the purport of the claim.

3. Determination

(a) Articles 6 and 11 of the Standardized Contract Regulation Act;