It seems to contradict the ultra-nationalist ideology of the Japanese government around the time of World War 2.
To clarify, I'm not talking about technological, military and administrative innovations that were necessary to stand up to Western powers, I'm talking about the superficial trappings of Westernization that had been adopted during the Meiji Restoration like classical music, Neoclassical architecture, and western military uniforms.
Interesting question. I do not have an answer for you, but one thing to keep in mind is that, at least during the early period of the Japanese empire, "modern" (Western) attire worn by Japanese was often a means of recognizing and establishing power between colonized and colonizer:
In the minds of colonizers, the inferior habitus of the colonized was reflected in the inferiority of their clothing, their cuisine, their social and work ethics, and even their language." (Mark Caprio, Japanese Assimilation Policies in Colonial Korea, 1910-1945, p. 12)
The wearing of Western styles of dress had meanings in addition to modernity and nationality/citizenship. In the late nineteenth century, Western-based dress was used to project (a gendered notion of) Japanese power. (82)
Although Japanese men in the colonies did not confine their clothing choices to yokufu [western style], often wearing Japanese kimono at home or even in public, their tendency to wear Western styles, especially in the shape of uniforms of professionalism...was not only a reflection of the growing naturalness of Western styles but also a way of distinguishing the 'natives' from modern Japanese. (86-87)
You have to understand in the post Meji Restoration era Japan was characterized by the Japanese trying to fit in as a Western Style power(Later on in the 30's the Japanese became militant and anti-western which was best showcased in ww2 with the co-prosperity sphere).while still retaining their Japanese heritage. The Japanese massacred Chinese prisoners during the first Sino-Japanse war but then treated the Russian pows taken during the Russo-Japanese war relatively well. This was all done to impress the western powers and "fit" in.
The desire to fit in was part of the reason for western style clothing, but it was also practicality. The Japanese were once a people that valued tradition over practicality but the leaders of post meji Japan realized that if Japan were to succeed on the national stage and have an army that could compete with the bigger powers they needed to adopt modern clothing, weapons, and modern army doctrines. They even banned their iconic Samurai swords because they were impractical and required two hands to use (For foot soldiers anyways) . So even though Japan became more militant the practical aspects and the desire to "fit in" didn't disappear.
Source:
"Japan's Imperial Army: Its rise and fall" Edward Drea
The Meiji Restoration: W. Beasley