The appeal is dismissed.

The costs of appeal are assessed against the Plaintiff.

The grounds of appeal are examined.

1. As to the assertion of misapprehension of legal principle

A. Article 250(2)2 of the Debtor Rehabilitation and Bankruptcy Act provides that the rehabilitation plan does not affect any security provided by any person other than the debtor for any rehabilitation creditor or any rehabilitation secured creditor.

This provision provides that even if the debtor's obligation is exempted or changed according to the rehabilitation plan, the obligation of the surety shall not be exempted or changed.

Here, "security provided by any person other than the debtor for rehabilitation creditors or rehabilitation secured creditors" refers to a security right that a rehabilitation creditor, etc. holds as the secured claim for the debtor's claims for a third party's property.

In light of the purport of the aforementioned provision, even in cases where an obligee’s right is forfeited or modified pursuant to Articles 251 and 252(1) of the Debtor Rehabilitation Act, the said provision does not affect the obligee’s right to secure another’s property by having forfeited or altered claims under Article 250(2)2 of the Debtor Rehabilitation Act (see, e.g., Supreme Court Decision 2003Da18685, May 30, 2003). The same applies to cases where there is a third party purchaser who, prior to the commencement of rehabilitation procedures, acquired the ownership of mortgaged real estate that had been mortgaged by the obligee as the secured claim against the obligor,

Therefore, in the event that rehabilitation procedures commence for the debtor, the mortgage held by the creditor on the real estate acquired by the third-party purchaser constitutes "security provided by any person other than the debtor for the rehabilitation creditor or the rehabilitation secured creditor" under Article 250 (2) 2 of the Debtor Rehabilitation Act, and thus, the rehabilitation plan does not affect this.

In addition, even if the creditor's right is forfeited or changed in the rehabilitation procedure, it is against the third purchaser of the forfeited or changed claim.