The Japanese monarchy is held in greater reverence than the British monarchy. No Japanese emperor influenced politics in the 20th century. For a while, both Britain and Japan had women speakers.
Japan now uses proportional representation in part.
Japanese prime ministers typically serve short terms. The prime minister is the locus of power in Japan. Japan's Liberal Democrats barely cohered as a party. Most of Japan's new parties are LDP spinoffs. Divisions within the LDP are largely ideological.