There are certainly similarities in terms of the ideologies, but I would argue they are mostly superficial similarities. The idea of 'fascism' is difficult to define and problematic because of the various ways in which it is used, and I think a broad strokes and loose definition does more to hide the important differences and unique characteristics between different examples of so-called 'fascism'.

Ideas within militant ultra-nationalism (the term I prefer to use, but there are other variants) in Japan certainly did involve concepts of racial superiority and supremacy, militarist and corporatist values, and the glorification of war and territorial expansion which seem reminiscent of Nazism or fascism. There were certainly those within Japan that advocated something of a variant of national socialism, and attempts at totalitarian-like social controls. However, an important difference is that there is much less cohesion within militant ultra-nationalism and a whole range of different squabbling groups and movements making up a fractious informal coalition. Even at the highest level of government and the military, there were at least two major factions of militarists at odds with each other (the Kodo-ha and Tosei-ha). That isn't to say factions and factional conflict didn't exist in other states, but more importantly perhaps in Japan, there was never any real central party or party-like structure which bound everything together. The militarists dominated Japan through control of the high levels of civil and military government positions and as an informal group rather than a formal party structure.

However, I say 'totalitarian-like' because while the militarist governments of Japan between 1936 and 1945 utilised propaganda, state intimidation and education to attempt to both control and sway the population, they were never able to succeed in implementing the level of totalitarian control present in other states. There was an attempt stated by Prime Minister Konoye in 1940 to establish something like a mass party in the Imperial Rule Assistance Association and the abolition of political parties and other civil organisations, but this existed as a mass party only on paper rather than in reality. The form of government established in 1889 continued to operate right through until the surrender, and there was even an election in 1942.

Also important is that the militarists never really swept away the existing state or ideologies but rather co-opted them. They utilised existing ideas of Imperial power and quasi-absolutism to their own ends rather than creating a new state. The Meiji Constitution remained in force and this document created an almost all-powerful emperor and executive. However, since the Emperor should not involve himself in actual political affairs, his advisers undertook these quasi-absolute powers on his behalf. What happened from the early 1930s is that the militarists placed themselves in a position to be those political advisers.

I'd also note that 'first half of the 20th century' is far too wide, and the militarist period of government ran 'officially' from 1936 through to August 1945 (although they start being a real force and power from 1931). The oligarch-dominated government established in 1868 with the Restoration and formalised in the 1889 Constitution largely continued until Meiji's death in 1912. However, his son and successor Taishō suffered from physical and mental illnesses and was unable to take an active role like his father, and this was coupled with the oligarchs starting to die off. The period 1912-25 is often referred to as 'Taishō democracy', and was a period of growing power for the elected Diet and political parties (although some of the problems and corruption of this helped the militarists largely backed by the rural poor).

There used to be an old debate in the field about whether wartime Japan was "fascist" or not but the rough consensus is that it totally depends on your definition of fascism. For what's it worth, the politics of wartime Japan was incredibly complex, certainly much more complicated than the common picture of "militarists" (itself a vague and meaningless term created by the Allied powers for war crimes prosecution) suddenly seizing power from a peaceful civilian government. In reality, the military was more like first among equals as at least half a dozen powerful elite institutions viciously at times struggled for power and never quite succeeding. Some scholars call this "limited pluralism." Publicly all elites pretended everything was hunky-dory and unified behind the emperor.