Serious question: what do you mean with "back" to democracy? I have never thought of either shogunates or the imperial development after Meiji restoration as "democractic". Is there a significant democractic era in Japan somewhere before?

Yes, absolutely. Prewar democracy in Japan was a complicated thing. It was largely controlled by elites from the Meiji to early Showa periods, but in the late 1920s universal male suffrage was extended with one huge caveat - the Communist Party was outlawed and police and intelligence services were given carte blanche to lock up, torture and kill leftists unless they publicly rescinded their views. While these acts largely succeeded in destroying opposition, defacto military rule was only put in place during the late 1930s.

Japan’s modernization, grappling with democratic and populist forces, and unfortunate collapse into fascism is some fascinating history to read about. “Japan in Crisis: Essays on Taisho Democracy“ is a good starting point.

Probably a frenchman nostalgic of the Republic of Ezo :-)

https://en.wikipedia.org/wiki/Republic_of_Ezo

Yes the Last Samurai had a kernel of truth, but it was not about an American guy, it was a bunch of French officers who deserted to help the Shogun in exchange of him proclaiming a republic. It has all the elements of an epic movie, including a desperate boarding of an ironclad by a samurai-French force that was repelled by a gatling gun: https://en.wikipedia.org/wiki/Battle_of_Miyako_Bay

Check out search results for "Taishō democracy".

Well, yes, but was it significant enough to warrant the post-1945 change as "back to democracy"? I feel that is pretty doubtful.

As Wikipedia puts it: Overall, during the 1920s, Japan changed its direction toward a democratic system of government. However, parliamentary government was not rooted deeply enough to withstand the economic and political pressures of the 1930s, during which military leaders became increasingly influential.