The appeal is dismissed.

The costs of appeal are assessed against the plaintiff (Counterclaim defendant).

The grounds of appeal are examined (to the extent of supplement in case of supplemental appellate briefs not timely filed).

1. As to the ground of appeal No. 1, the parties may freely determine whether to conclude a contract in accordance with the principle of freedom of contract and what content and method, and may supplement the contents of the contract by agreement after the conclusion of the contract.

In order to supplement the contents of the contract after the formation of the contract, there must be a mutual agreement between the parties to supplement the contract, explicitly or implicitly.

If, after the conclusion of a contract, one party sent a document that contains any matters different from the contents of the contract, and the other party does not raise an objection to the change in the contents of the contract, it shall be deemed that the other party explicitly consented to the change in light of the type and nature of the transaction, trade practice, details and form of the dispatch document, attitude of the other party, etc.

In this case, if the change results in an important change in the terms of a contract already concluded, such implied consent shall not be easily recognized.

The lower court recognizes the following facts.

① On October 18, 2007, the Plaintiff (Counterclaim Defendant; hereinafter “Plaintiff”) entered into a contract with the Defendant (Counterclaim Plaintiff; hereinafter “Defendant”) to sell used goods in KRW 165,00,000, the textile processing machinery of this case, which is used goods, to the Defendant (hereinafter “Defendant”) and paid the price in a way that the Plaintiff deducts USD 0.5 per cent of the original unit from the original unit price purchased by the Defendant.

② The Plaintiff decided to transport and install the textile processing machinery of this case to a factory operated by the Defendant in China, and the cost of the removal of machinery.