29. What are the eligibility criteria for political parties to receive public funding?

Source: 
政党助成法, 1994 (2022改正)
Political Party Subsidy Act, 1994 (as amended by Act No. 68 of 2022)

第二条　この法律において「政党」とは、政治団体のうち、次の各号のいずれかに該当するものをいう。
一　当該政治団体に所属する衆議院議員又は参議院議員を五人以上有するもの
二　前号の規定に該当する政治団体に所属していない衆議院議員又は参議院議員を有するもので、直近において行われた衆議院議員の総選挙における小選挙区選出議員の選挙若しくは比例代表選出議員の選挙又は直近において行われた参議院議員の通常選挙若しくは当該通常選挙の直近において行われた通常選挙における比例代表選出議員の選挙若しくは選挙区選出議員の選挙における当該政治団体の得票総数が当該選挙における有効投票の総数の百分の二以上であるもの

Article 2. In this Act, “political party” means a political organization that falls under any of the following items:
(i) One that has five or more members of the House of Representatives or members of the House of Councillors belonging to said political organization;
(ii) One that has members of the House of Representatives or members of the House of Councillors who do not belong to a political organization falling under the preceding item, and and in the most recent general election for members of the House of Representatives, either the election of members elected from single-seat constituencies or the election of members elected by proportional representation, or in the most recent regular election for members of the House of Councillors, or in the most recent proportional representation election or single-seat constituency election for members of the House of Councillors held immediately prior to said regular election, the total number of votes cast for said political organization constitutes two percent or more of the total number of valid votes cast in said election.

Representation in elected body and share of votes in previous election both matter.  A party should (1) have five or more members in the House of Representatives or the House of Councillors or (2) got more than 2% of the votes in the most recent national election.