This is admittedly post-1900, but it's a period of time you can draw inspiration from. I've always found the period of
"Taisho Democracy" to be a particularly fascinating one. Long story short, between an oligarchic Meiji period and militaristic Showa period, we have a brief interlude in the 20s that's liberal, cosmopolitan, and consumerist.
A non-expansionist Japan might have to come through with a stronger Qing Dynasty. Perhaps an alternate Gaspin Coup of 1882 could result in an earlier, pro-Japanese Korea, which forces the Qing to double down and modernize? Without the pressure of the Russians, British, and Americans breathing down East Asia's neck, the Japanese may be less inclined to push for their own Pan-Asianist goals. Similarly, an earlier placement of Japan, Korea, and China on equal footing with the Europeans (at least within the theater of East Asia) may forestall Japanese expansionism. Bear in mind that much of the early Japanese expansion (Korea, Port Arthur, Sakhalin) was, in part, a reaction to perceived European threats to Japanese (and East Asian) independence. Should there be a less pressing threat of European imperialism, I imagine the urgency of a Pan-Asian union (and, later, a Greater East Asia Co-Prosperity Sphere) would be drastically reduced.