The Supreme Court recently stated that under case number 2005DU15595Civil Code Section 382 Article 2 cannot be applied for the right to claim division of the matrimonial property by a surviving spouse of a de facto marriage at the termination of the marriage by the death of one partner. Since then, the academic world has openly questioned if it is appropriate to have no protection in the case of a de facto marriage termination by death of one party given that one is entitled to claim for the separation of matrimonial property if both parties are alive at the termination of marriage. In Case number 2008SU105 one de facto marriage party claimed the end of de facto marriage and the division of property while the other party was in a comma. The Supreme Court ruled in favor of the right to claim for separation of property on the grounds that the marriage was terminated by one of the parties before the death of the other party. This decision has set a precedent for filing a law suit for the separation of property when one of the parties experiences a critical health condition. This is undoubtedly unreasonable. To discourage such a situation it is therefore necessary to enact an alternative solution to protect the surviving spouse or the heir of the dead party at the termination of a de facto marriage by the death of one partner. This study reviews the established theories and proposes the use of private opinion to find a means to protect the surviving spouse or the heir of the dead party who is in a state of legal limbo. The scope of protecting de facto marriage fundamentally cannot exceed that of legally binding marriage. The parties in common law marriage are protected by inferring the property division claim system when their relationship is terminated. Then when the relationship is ended by the death of one party, liquidation of the property jointly formed during the period marriage should be made within the range of the inheritance system. This should be applied not only to the surviving party of the de facto marriage but also to the dead party. On the premise of the above mentioned logic, this study aims to find a way to mediate the parties in a de facto marriage relationship by the legal principles of inheritance. It starts from the review of the unique system that one can request to verify if an actual de facto marriage relation exists(사실상혼인관계존부확인청구제도) in family law. If the Ministry of Justice tries to have a broader view on the existing policy with the case where one partner in the de facto marriage is dead, the surviving partner can be recognized as an official spouse of the de facto marriage according to the kind of lawsuit to confirm the existence of de facto marriage(사실상혼인관계존재확인의소) even without the other legislative measures. Once the surviving partner is recognized as an official spouse, the spouse can be entitled with the right to claim matrimonial property by applying the inheritance system. After the death of an inheritor, a spouse from a de facto marriage deserves a part of the inherited property for the portion of his/her contribution toward the formation of matrimonial property in the same manner as the spouse from a legal marriage. With the appearance of diverse forms of cohabitation, to respect self-determination and to uniformly admit the spouse inheritance for all parties in de facto marriage, it is suggested to protect the surviving parties with matrimonial property personally and optionally only when one files the kind of lawsuit to confirm the existence of de facto marriage(사실상혼인관계존재확인의 소).