As the "Taisho political crisis" has shown, the political situation of the early Taisho period featured a number of political movements of a pluralistic nature. This and the related "Kei-En (Katsura-Saionji) system of the government" led to a situation of extreme instability. The Yamagata Aritomo faction was thus unable to prevent the infighting of the political factions in the bureaucracy. At the same time, the confrontation in the Seiyukai Party between Hara Takashi and Matsuda Masahisa was brought to the surface. Thus, neither of them had enough power to form a main stream in the bureaucracy and the diet. Accordingly, there arose possibilities of the formation of various powers. And as the result of the rise of the Satsuma clique and the Doshikai Party, it was difficult for any group to make a cabinet easily. On the other hand, the Genros were unable to function of controlling among groups. In this essay, I will discuss the structure of the Second Okuma cabinet which appeared in the middle of this complicated political situation, and the political tactics of the Genros and the government parties (Doshikai, Chuseikai, etc.), so as to make clear of the political system of the early Taisho period. Among the Genros, Yamagata and Inoue Kaoru strongly supported the Okuma cabinet. They tried to cooperate with non-Seiyu diet members (the government party members of the Okuma cabinet) and restore their political power. On the other hand, the parties in power sought to establish the government based on political parties. But, there existed the opposition between a group of Kato Takaaki and Oura Kanetake and of Ozaki Yukio and Oishi Masami in persuit of leadership. There was inclination of the linkage of Yamagata with the former group, and Inoue with the latter. This reciprocity of confrontation and cooperation became apparent in the process of selecting the Home Minister, deciding foreign policies, dissolving the Diet, and uniting government parties. As the result of these, the Kato-Oura group took over the leadership of the Okuma cabinet. However, the Kato-Oura group was duly counterattacked by other political groups. Due to the efforts by Ozaki, Justice Minister, the Oura bribery case was brought to light, and then Oura had to resign from his office in August 1915. Soon after that, other members of the Kato-Oura group mostly left the cabinet. Although it is not discussed in this essay, the Genros could not reconcile with the government parties against their expectations. Rather, two groups in the government parties weakened their confrontation and organized newly the Rikken Kenseikai Party. In this essay, I would like to point out following points. First, the explanation until now that the Okuma cabinet was merely a puppet of the Genros is wrong, and the power of the government parties should be valued more. Secondly, although usually only the Seiyukai has been acclaimed for its activities, the non-Seiyu parties also need to be estimated as has conducted important roles during this period.