One of the aims of this study is to point out the fact that the victory of the Democratic Party of Japan (DPJ) in the 2007 election of the House of the Councilors further promoted the bi-party political structure between the LDP (Liberal Democratic Party) and the DPJ. To this end, the paper deals with a few cases to illustrate the changes of the Japanese politics since the election, in an effort to look into its political implications and the perspective it offers. The election result in 2007 served as an occasion to bring the opposition to the center stage in political and academic terms alike, although they had not been regarded as a significant player in the Japanese politics until that time. The limelight was cast because the potentials of the political power of the House of Councilors was brought into reality thanks to the fact that one of the opposition parties, DPJ, took up the majority. Notwithstanding the fact that the Upper House is vested with the function to oversee the administration and the Lower House, its constitutional power has not been effectively utilized from the advent of the 1955 system to 2007 because only one party has been selected as the majority in both chambers of the Japanese parliament during this whole period. If the Upper House is to be able to carry out its function in the real politics, the ruling party and one of the oppositions need to take up the majority in each house, which indeed took place in the aforementioned 2007 election. The result was a political effect similar to the divided government under a presidential system. In other words, political stalemates began to be witnessed when policies and bills put forward by the government or the ruling party bumped into the opposition by the DPJ, the majority party of the House of Councilors. The key assertion of this paper is therefore that, as the DPJ is securing a stronghold for a power takeover based on its legislative activities with the Upper House serving as the stage, it can be said that a bipartisan system enabling two major parties handing over power among them is taking root in Japan.