法令翻訳 http://www.japaneselawtranslat...amp;page=5

(社員の責任を変更した場合の特則)
第五百八十三条   有限責任社員が無限責任社員となった場合には、当該無限責任社員となった者は、その者が無限責任社員となる前に生じた持分会社の債務についても、無限責任社員としてこれを弁済する責任を負う。

Special Provisions in Case of Members' Liability Change
Article 583   In cases where a member with limited liability has become a member with unlimited liability, the person who has become such member with unlimited liability is also liable as a member with unlimited liability for the performance of the obligations of the Membership Company that arose before such person became a member with unlimited liability.

有限責任社員（合同会社の社員を除く。）が出資の価額を減少した場合であっても、当該有限責任社員は、その旨の登記をする前に生じた持分会社の債務については、従前の責任の範囲内でこれを弁済する責任を負う。

Even in cases where a member with limited liability (excluding members of Limited Liability Company) reduce the value of the contributions, such member with limited liability is liable to the extent of the member's pre-existing liability for the obligations of the Membership Company that arose before the registration to that effect.

無限責任社員が有限責任社員となった場合であっても、当該有限責任社員となった者は、その旨の登記をする前に生じた持分会社の債務については、無限責任社員として当該債務を弁済する責任を負う。

Even in cases where a member with unlimited liability has become a member with limited liability, the person who has become such a member with limited liability is liable as a member with unlimited liability for the performance of the obligations of the Membership Company that arose before the registration to such effect.

前二項の責任は、前二項の登記後二年以内に請求又は請求の予告をしない持分会社の債権者に対しては、当該登記後二年を経過した時に消滅する。

The liability under the preceding two paragraphs to the creditors of the Membership Company who do not make their claims, or do not give an advance notice of their claims, within two years from the day of such registration is extinguished when two years have elapsed from the day of the registration in the preceding two paragraphs.