Liberalism in Japan
Japanese liberalism formed in the nineteenth century as a reaction against traditional society. In the twentieth century 'liberal' gradually became a synonym for conservative, and today the main conservative party in the country is named Liberal Democratic Party (Jiyu Minshuto). The Democratic Party (Minshuto) was considered in part a left-of-center social-liberal party, as are most parties which derived from it. The liberal character of the Liberal League (Jiyu Rengo) is disputed, as it is also considered to be conservative by some. Liberals in Japan are generally considered united by one major factor: their opposition to changing the post-World War II constitution forbidding the creation of a national military. This article is limited to liberal parties with substantial support, proved by having had representation in parliament. The sign ⇒ means a reference to another party in that scheme. For inclusion in this scheme it isn't necessary that parties labelled themselves `liberal`.

The timeline

From Public Society of Patriots until Constitutional Politics Party
1874: Liberals founded the Public Society of Patriots (Aikoku Koto)
1881: The Aikoku Koto is continued by the Liberal Party (Jiyu-to)
1891: The Jiyuto is renamed into Constitutional Liberal Party (Rikken Jiyuto)
1898: The Constitutional Liberal Party merged with the ⇒ Progressive Party into the Constitutional Politics Party (Kenseito)
1898: A faction seceded as the ⇒ Constitutional Center Party
1900: The party is taken over by the oligarchy and renamed into Constitutional Political Friends Association (Rikken Seiyukai)

From Constitutional Progressive Party to Reform Club
1882: The Constitutional Progressive Party (Rikken Kaishinto) is formed 
1896: The party is continued by the Progressive Party (Shinpoto)
1898: The party merged into the Constitutional Politics Party (Kenseito)
1898: This party fell apart and a faction of the Kenseito formed the Authentic Constitutional Party (Kensei Honto), renamed in 1910 into the Constitutional National Party (Rikken Kokuminto)
1913: A faction seceded as the ⇒ Constitutional Association of Allies
1922: The Constitutional National Party is renamed Reform Club (Kakushin Kurabu)
1920s: The Reform Club merged into the Constitutional Association of Political Friendship

From Constitutional Association of Allies to Constitutional Democratic Party
1913: A faction of the ⇒ Constitutional National Party formed the Constitutional Association of Allies (Rikken Doshikai), renamed Constitutional Association (Kenseikai) in 1916
1927: The Constitutional Association merged with the ⇒ Authentic Constitutional Party of Political Friendship into the Constitutional Democratic Party (Rikken Minseito)
1940: The party is dissolved by the regime

Authentic Constitutional Party of Political Friendship
1924: A faction of the Constitutional Association of Political Friendship formed the Authentic Constitutional Party of Political Friendship (Seiyu Honto)
1927: The party merged into the ⇒ Constitutional Democratic Party

From Renewal Party to Liberal Party (1993)
1993: A liberal faction of the conservative Liberal Democratic Party (Jiyu-Minshuto) seceded as the Renewal Party (Shinseito)
1994: The Renewal Party merged with other factions into the New Frontier Party (Shinshinto)
1997: The New Frontier Party fell apart into many parties, among them since 1998 the Liberal Party (Jiyuto), but also the Good Governance Party (Minseito), the New Fraternity Party (Shinto-Yuai) and the Democratic Reform Party (Minshu-Kaikaku-Rengo)
2000: Dissidents of the Liberal Party formed the New Conservative Party (Hoshuto)
2003: The Liberal Party merged into the ⇒ Democratic Party of Japan

New Party Harbinger
1993: A liberal faction of the conservative Liberal Democratic Party (Jiyu-Minshuto) seceded as the New Party Harbinger (Shinto Sakigake)
1996: Most members co-found the ⇒ Democratic Party of Japan
1998: The party evolved in conservative direction, renamed into Harbinger (Sakigake) and further renamed in 2002 into Green Assembly (Midori No Kaigi)

Democratic Party of Japan
1996: Dissidents from the New Party Harbinger and the Social Democratic Party founded the Democratic Party of Japan (1996) (Minshuto)
1998: The party merged with the Good Governance Party (Minseito), the New Fraternity Party (Shinto-Yuai) and the Democratic Reform Party (Minshu-Kaikaku-Rengo) to form a new, enlarged Democratic Party of Japan (1998) (Minshuto, 民主党)
2003: The Liberal Party merged into the party
2016: The Democratic Party of Japan merged with Japan Innovation Party and Vision of Reform to form the Democratic Party (Minshinto, 民進党)

CDP and DPP
2017: The Constitutional Democratic Party of Japan (Rikken Minshuto, 立憲民主党) is formed as a liberal split from the Democratic Party.
2018: The remaining Democratic Party merged with Kibō no Tō and form the Democratic Party for the People (Kokumin Minshutō, 国民民主党).

Liberal leaders

Itagaki Taisuke - Hamaguchi Osachi