The appeal is dismissed.

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

The grounds of appeal are examined.

1. As to the allegation in the grounds of appeal as to the res judicata of the offset defense

A. 1) Article 216 of the Civil Procedure Act provides that a final and conclusive judgment shall have res judicata only in cases where it is included in the text of the judgment, and that, in principle, a final and conclusive judgment does not have res judicata effect. On the other hand, as the only exception, whether a claim alleging a offset under paragraph (2) is constituted or not, as the only exception, has res judicata effect only on the amount set up against offset. The purport of recognizing res judicata effect in the judgment of the court as to the allegation of offset is, notwithstanding the judgment among the reasons for the judgment above, if the judgment of the court does not recognize res judicata effect, the purport of recognizing res judicata effect is only to the opposite claim (or automatic claim, hereinafter referred to as “sub

(2) If a set-off claim is deemed to have res judicata effect on the judgment on the claim of set-off, the other party who has asserted a set-off may suffer disadvantage by double exercise of the opposite claim, and as a result, the judgment on the existence of the plaintiff's claim based on the premise of a judgment on the set-off claim may cause incompetence, which would result in a judgment on the existence of the plaintiff's claim based on the premise of a judgment on the set-off claim, and thus, it would be to prevent such a judgment (see Supreme Court Decision 2004Da17207, Jul. 22, 2005). In a case where a judgment on the set-off claim is recognized, it refers to a case where the passive claim, which is the subject of the claim of set-off, is a subject matter of lawsuit, or where it appears to be substantially identical (see, e.g., where the plaintiff files a lawsuit seeking a set-off

(Supreme Court Decision 2004Da17207). On the other hand, a set-off defense as a means of defense in litigation is ordinarily a passive claim.