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

Defendant B’s 49,370,000 won and 39,370.

1. The reasoning for this part of the judgment of the court is the same as that of Paragraph 1 of Article 420 of the Civil Procedure Act, and this part of the reasoning of the judgment of the court of first instance is cited.

2. Determination

A. According to the above facts, it is reasonable to view that Defendant B bears the obligation under each of the contracts in this case against the Plaintiff, and Defendant C is jointly and severally guaranteed the obligation under the agreement in each of the contracts in this case against the Plaintiff. 2) Furthermore, where the purpose and form of the principal obligation are changed within the extent that the substantial identity of the principal obligation is not lost between the Plaintiff and the Plaintiff without the guarantor's knowledge after the establishment of the guarantee agreement and at the same time the burden of the principal obligation is reduced and mitigated, the guarantor is liable to guarantee the principal obligation according to the contents of the reduced and mitigated principal obligation. However, where the contents of the principal obligation are expanded and reduced due to the change, the guarantor is not liable to guarantee the principal obligation in accordance with the contents of the principal obligation prior to the change, but the guarantor is only liable to guarantee the principal obligation prior to the change. In addition, where the creditor extended the period of payment to the principal obligor without the guarantor's consent, it cannot be deemed that it has increased the obligation of the guarantor.

(2) The Defendant C’s guaranteed obligation also becomes due and payable on February 28, 2017, inasmuch as the Defendant C’s principal obligation was reduced due and its principal obligation was extended on February 28, 2017 and its principal obligation was reduced. Thus, even if the Defendant C’s second memorandum was written between the Plaintiff and the Defendant B without Defendant C’s consent, each obligation of KRW 21,370,000,000 of the content of the commitment performance (1) and the content of the commitment performance (2) pursuant to the said second memorandum, and each obligation of KRW 18,00,000,000 of the content of the commitment performance (2) was reduced.