Ever wonder why so many Japanese politicians are old and that the only new faces tend to be their progeny? There are a number of cultural explanations for this phenomenon, but there's also a financial one. It's called the kyotakukin, or deposit, system.
To run for any office in Japan, whether national or local, a person must deposit a certain amount of cash with the relevant election authorities. If the person wins, the deposit will be returned, but if the candidate loses and in the process fails to garner a certain percentage of the votes cast, he or she forfeits the money. The amounts required are high, and for national office almost prohibitively so. Candidates for prefectural and municipal office need to pay deposits of between ¥300,000 and ¥600,000, depending on the size of the constituency. However, candidates for the Lower House of the Diet have to deposit ¥3 million for a constituency seat and ¥6 million for a proportional seat. Constituency seats are decided for an electoral district simply by the number of votes cast in the district. Proportional seats are decided by the portion of votes a particular party receives on the proportional part of the ballot.
Many candidates, in order to guarantee success, run in both contests, because while they may lose in the constituency race, their party may gain a large enough portion of votes to allow them to be swept into office on the proportional ticket. In that case they have to pay deposits for both seats, meaning ¥9 million. If a constituency candidate doesn't garner at least 10 percent of the total votes, he or she has to forfeit the deposit.