Among the plaintiffs, the part concerning each claim for damages is reversed, and this part of the case is applied.

1. As to the grounds of appeal on the Plaintiffs’ claim for restitution of unjust enrichment, the lower court rejected all the Plaintiffs’ assertion on the following grounds: (a) the instant currency option contract is invalid on the grounds of a violation of the Regulation of Standardized Contracts Act, civil law, or an unfair legal act; (b) the instant currency option contract was cancelled on the grounds of deception and mistake as to the value of options, fees, and compatibility of the foreign currency or foreign exchange hedging; and (c) the instant currency option contract did not have the Defendants’ call options; (d) the Defendants did not notify the Defendants of the exercise of the call option; and (e) the Defendants renounced the third currency option contract on the grounds of change in circumstances, such as increase in the scope of foreign exchange fluctuation that occurred after the conclusion

In light of the relevant legal principles and records, the above judgment of the court below is just, and there is no violation of law as otherwise alleged in the ground of appeal.

Meanwhile, according to the records, the lower court did not explicitly determine the Plaintiffs’ assertion that the instant currency option contract is null and void in breach of the principle of trust and good faith, as it is contrary to justice and equity to maintain the validity of the instant currency option contract which is inappropriate for the Defendants to exchange hedging.

However, in light of the probability of exchange rate fluctuations, each currency option contract of this case is a partial exchange hedge product that has equal expectation interests between the Plaintiffs and the Defendants, and thus, it cannot be said that the contract contravenes the principle of trust and good faith on the ground that it cannot achieve the purpose of exchange hedging in a certain exchange rate fluctuation section.

Therefore, the court below's omission of judgment is clear that the plaintiffs' above assertion is dismissed.