I think some of the arguments here are interesting. A British model instead of a Prussian model of parliamentary system might help, but preventing the ultranationalism of the early 1930s does well also. Manchuria will be a Japanese interest if not outright possession, but making it so in the 1910s only accelerates the Japanese interest in taking over the rest of the country.
Japan did have a parliamentary system based on the British model; initially, the Imperial Diet was based on the Westminster system. However, due to the rise of militarism, the power of the Diet gradually declined; there were times when the Diet would be strongly opposed to a law; but pressure from the military meant that they would have to grit their teeth and pass it.
I would think that by having a stronger China one might offset Japanese ambitions, especially a China capable of fielding a navy that might create an East Asian analog to Brazil and Argentina: two second-tier nations that really do not like each other, have a common border, and a serious grudge.
It's also worth mentioning that for a time, China did have a navy comparable to that of Japan, before the First Sino-Japanese War. However, during that war, the Japanese repeatedly and decisively defeated the Beiyang Fleet, due to the endemic corruption in the Chinese military making the Beiyang Fleet completely unfit for any sort of combat operations. Similar problems afflicted the army, and were a major factor in its total defeat on land. Corruption and hidebound reaction were probably the biggest obstacles to China emerging as a serious competitor to Japan.