2. The costs of appeal are borne by the Defendant (Counterclaim Plaintiff).

Accordingly, since only the defendant filed an appeal regarding a counterclaim among the judgment of the court of first instance, this court makes a decision only on a counterclaim claim.

2. Determination on the cause of the counterclaim

A. On June 2003, the Defendant asserted that the Defendant, instead of paying retirement allowances between the Plaintiff and the Plaintiff, agreed to pay 50% of the national pension and health insurance premiums to the Defendant, an employer, who is an employer, and paid on behalf of the Defendant by May 31, 2014, and the employment insurance premium was paid on behalf of the Defendant.

However, if the money paid by the Defendant as above is invalid as retirement allowance, the Plaintiff would have made unjust enrichment, and thus, the sum of KRW 13,907,780 paid by the Defendant on behalf of the Plaintiff should be returned as unjust enrichment.

B. Determination 1) If an employer does not recognize the validity of the payment as a regular retirement allowance even though the employer actually paid the amount in the name of the retirement allowance to an employee, and it is not recognized that the payment as a wage under Article 18 of the former Labor Standards Act is not effective, it is reasonable from the perspective of fairness to view that the employer should return the amount in the name of the retirement allowance received by the employee as unjust enrichment (see, e.g., Supreme Court en banc Decision 2007Da90760, May 20, 2010). However, considering the legislative intent of the retirement allowance system, the above legal principle is applied under the premise that the actual division agreement exists between the employer and the employee, and the pertinent agreement entered into between the employer and the employee is determined as wages.