【Main Issues and Holdings】
[1] In a case where a party to whom a favorable judgment has been rendered files a lawsuit on the same claim against the other party in the preceding lawsuit, whether there is an interest in the protection of right in the subsequent lawsuit (negative)
Whether this likewise applies when a party to whom a favorable judgment has been rendered from a foreign court, which meets the requirement for approval under Article 217 of the Civil Procedure Act, files a lawsuit on the same claim against the other party in the preceding lawsuit (affirmative)
[2] Standards for determining whether the requirements of “mutual guarantee” under Article 217(1)4 of the Civil Procedure Act are met, and whether the fulfillment of the requirements for approval of a foreign judgment are met falls under the subject matter of the court’s ex officio investigation (affirmative)