If you want personal recommendations, I recommend the Nambu, the Type 30, the Type 38, the Nagant, the Madsen and the Type 26 with the 37mm as a support gun
I mind you that he needs to look at the number produced. The Nagant for example had 2,000,000 units produced and was in service from 1986 to 1950 in Russia and Belgium. The page gives and average of 20,000 produced each year. Say they produced them untill 1930, which is near the year that they were ''obsolete'' and replaced by better variants. That's 44 years or roughly 45,000 models a year. We're in 1910 at the moment so that makes 1,080,000 produced by then. If we're claiming what i'm using as a ''fact'' that is. I recall his army having 800,000 conscripts. That would only leave 280,000 pistols to be devided between Belgium and the Russian army, the latter being the one it was specifically produced for. Therefor it seems highly unlikely that he would have a high quantity of a sparesly produced pistol. (I'm aware you never said every soldier had one, but you did not include it as a support gun which made me assume it was part of the main armament.)
So basically, i'm being a buzzkill. But I love realism, and I think that people should take things like the above into account.
Edit: Japan would also never-ever supply weapons to any Chinees faction in that time, unless they were a proper Japanees puppet regime. I'm aware there are smugglers, but with the quantity produced of many of the weapons it's very unlikely he will have enough weapons to field such a large army.
Edit to the edit: You are also supplying him with fairly modern rifles, which is not very accurate. Try giving him the single shot old rifles from the 1880's and what not. Because that was much more common those days. There is a reason that the Japanees used Banzai charges against the Chinees on numerous occassions. Simply because they had one shot rifles and couldn't do much to repel the charges succesfully.
(I hope this helps, don't want to be a dick, just giving some information.)
Edit of the edit to the edit: Am I accepted by the way? My character sheet is 95% done, only the biography needs to be added. The rest has been finished, as accurately and historically correct as I could, I might add.