Seiji Osako, a moderate and former acting leader of the Constitutional Democratic Party of Japan, has suffered a significant defeat in Hokkaido's 8th electoral district, failing to regain his seat despite previously holding multiple political roles including vice-minister of internal affairs. At 66 years old, he aimed for a seventh term but faced a formidable opponent in Jun Mukoyama, a newcomer from the ruling Liberal Democratic Party, who had garnered momentum as a junior minister. Despite the challenges posed by Mukoyama's campaign, which capitalized on the ruling party's appeals and groundwork, Osako highlighted the risks of the current government's security policies, stating that voters should not grant them a blank check.

The results of this election mark a pivotal moment in Osako's political career, once a seasoned lawmaker who initially lost his seat during the 2012 elections but managed to return in subsequent years. The lack of a proportional revival illustrates the shifting political landscape in Japan. Osako's previous advantage of over 14,000 votes against Mukoyama in their last encounter confirms the degree of the electoral shift; this time, despite his appeals about national security issues, he was unable to replicate this success.

Following this setback, Osako's future in politics remains uncertain, as the implications of his defeat reflect broader challenges faced by the Constitutional Democratic Party and moderate factions within Japan. This loss may signal difficulties for the party in establishing a solid footing against the dominant Liberal Democratic Party, which continues to leverage its influence in shaping security policies and governance in the country.