The Japanese veto-gate structure could be about to get really interesting. Japan’s upper house, the House of Councilors (HoC) is quite powerful among upper chambers of parliamentary systems, but it does not have an absolute veto. Rather, on measures that require passage through both houses, its veto can be overridden by a two-thirds vote of the lower house, the House of Representatives (HoR).
It just so happens that the LDP and its coalition partner, the New Komeito, will have only 42.6% of the HoC seats after Sunday’s election, but the governing coalition has exactly 70% of the seats in the HoR since the 2005 election. (The LDP alone holds 63.5% of the HoR seats.)
As Robert Pekkanen notes in the previous thread, the opposition DPJ will have 45% of the HoC seats, and thus not enough to control the body on its own. However, it ran in an alliance in many districts with some of the successful independents and PNP candidates (also, in at least one case, with the SDP). It thus might be able to form a coalition to control the HoC, though (as Prof. Pekkanen also notes) it may choose not to do so.
In any event, the HoC veto and HoR override provisions will suddenly become quite relevant for policy bargaining. The only items over which the HoC has no veto are the selection or ousting of a Prime Minister (on which it also has no initiative), treaties, and the budget (where the veto is suspensory only: the HoR can override by majority after 30 days). The budget is, of course, a big piece of legislation on which not to have a full veto. But revenue and program authorization are ordinary legislation and thus require the consent of the two houses (or 2/3 of the HoR). (This is all based on my interpretation of a translation of Articles 59-61 of the Japanese constitution.)