All appeals are dismissed.

The costs of appeal are assessed against the Defendants.

The grounds of appeal are examined.

1. On the grounds indicated in its reasoning, the lower court determined that, even if an agreement on the payment of design compensation was concluded between the Plaintiff and the Defendants on the payment of design compensation, and the tender was not invalidated in accordance with the purport of the provision on the return of design compensation incorporated into the content of the agreement, insofar as there exist grounds falling under invalidation of the tender, the said person has the duty to return the design expenses before the discovery of invalidity of the tender, and confirmed the Defendants’ assertion that the

(3) If the Plaintiff’s assertion on the invalidity of the instant tender violates the principle of good faith or the principle of good faith, the Defendants ordered the Defendants to pay damages for delay at the rate prescribed by the Commercial Act and the Act on Special Cases Concerning the Promotion, etc. of Legal Proceedings from the date following the date the Plaintiff requested the return of the design compensation

The judgment below

Examining the reasoning in light of the record, the lower court did not err by exceeding the bounds of the principle of free evaluation of evidence in violation of logical and empirical rules, or by exceeding the bounds of the principle of free evaluation of evidence, contrary to what is alleged in the grounds of appeal, or by misapprehending the legal doctrine on commercial activities, such as contract formation, nature of payment of design compensation, validity of the provision on return of design compensation, contract interpretation and ratification, violation of the principle of trust and good faith, violation of the principle of trust and good faith, starting point of time for delay damages

2. Therefore, all appeals are dismissed, and the costs of appeal are assessed against the losing party. It is so decided as per Disposition by the assent of all participating Justices on the bench.