Peter Cave writes:

"[T]he deposit requirements. for candidates running for political office in Japan, especially for the Diet:.
seem a very significant deterrent to political participation (especially by those who are not personally wealthy or backed by wealth/business) and a threat to political competitiveness. I wonder if it also helps to explain why the DPJ failed to fight a significant number of Diet districts for some years."
(2012/11/07)

A forfeitable 3,000,000 yen deposit for a single-member district (SMD) in the House of Representatives (HOR) appears to be a significant deterrent against running for a Diet seat if you are out of work, have only illiquid assets if any, is unable to secure support from any of the established parties, and lack name recognition. If you do not belong to this demographic, you have other, more serious concerns.

An SMD bid is expensive. You must expect any candidate from a major party to spend up to the legal limit of
(19,100,000 + 15 x number of eligible voters in the
SMD) yen. Other candidates from established parties may spend less, but are highly likely to incur expenditures well above the 3,000,000 deposit. That limit would be
22,321,040 yen under the latest National Census, in Kochi District 1, currently the smallest SMD available to you. It would be significantly higher in any metropolitan SMD. You must be willing to spend a substantial amount of money yourself if you want to be competitive, or have some other compensating feature to your makeup, to which I will come back later.

Coming up with that kind money is not a problem if you have plenty of liquid assets; it's somewhat more problematic if you are married and need to take out a mortgage on the family home for that. (Some people do that, though, apparently.) In any case, the buck does not stop there. The official campaign period starts when the election is called, but you will have spent months if not years before that laying down the ground works of your official campaign, and that costs money too. Affiliation with an established party will alleviate your money concerns, but you will still be footing much of the bill.

It will also cost your time. Running for office, if you are serious, can be a full-time job. That means that you will have to suspend or otherwise drastically curtail your day job. That takes a huge leap of faith if you are a salaryman-unless you're say, a Panasonic employee and you're running as the labor union's candidate *wink wink* so you can go back to your day job if your bid fails. It's easier, of course if you are a doctor, dentist, lawyer or other professional with a well-established practice and can pick up where you left off if your bid is unsuccessful.

Name recognition can be a good substitute for the above. This is not a HOR SMD example, but Yukio Aoshima, a well-known writer/comedian/actor, tossed his hat into a Tokyo gubernatorial race as an independent, left the country in the days when there was no internet to speak of, and still won the race.

Of course, none of this matters if you're out-of-work and penniless, and the only campaigning that you intend to do is use the free TV broadcasting airtime that MIC gives to each of the candidates to hold forth on the subject of your choice: Legalize pot? Why not? Ah, but there's the matter of the 3,000,000 yen deposit. so what you need here is the support of the DPJ or some other party with street cred so you can get at least
1/10 of the effective votes cast in the SMD on the party name alone so you can get that money back.

I hope that this enough as an illustration of the following comment from Ellis Kraus:

"I think the high deposit requirement was put in mai[nl]y as a deterrent to discourage single issues micro parties and frivolous candidates from running."
(2012/11/07)

(For the right price, I will cover the regional proportional districts as well as the House of Counselors, all in more detail.)

Sidebar: A better place to look for a legally imposed financial barrier to new entries would be the Political Party Subsidies Act, under which the Ministry of Internal Affairs and Communications is distributing
32,014,332,000 billion yen this year to 11 political parties passing thresholds based on based on the number of Diet members they have and/or votes they received in the last lower house and last two upper house elections. (The Japan Communist Party refuses to accept the money on principle.) That can buy a lot of hay; in fact, this averages out to 44,341,180 yen worth of hay per Diet member. That means that you're spotting the LDPs and Komeitos a huge cash advantage when you're starting up a new party. It also explains the financial appeal of (presentable) B- and C-list Diet members to the latest crop of start-ups. (The arrangement is also likely to put regional micro-parties (four Diet members or less) at a disadvantage.)