Oh, they'll get something out of this war, but Indochina is highly unlikely, yes.A thought on Japan's 21 demands. The main reason Japan leveled them was that England, France and the rest of Europe was wrapped up in war. ITTL Europe minus england gets wrapped up in war but there is still opportunity for Japan to get Chinese consessions with angering England or the US.
Russia holds large territories in Manchuria and is now bogged down in Europe with Germany going with a East first policy. What if Japan tired to get Russian concessions bent to them (like german ones in OTL). Japan remembers a successful war against Russia 9-10 years ago and heres a chance to expand north from Korea and get resources in Manchuria. England had a treaty with Japan and didn't like Russia (India, the Straights etc.) I can see a Nudge, Nudge, Wink, Wink here.
Also there is a chance to pick up some French concessons later after Germany turns on them. Instead of Japan picking up Shantung and German Islands Japan picks up Fiji and some southern Chinese ports. Indochina is too ASBish or a Japan wank
Japan made a ton of money for little effort in OTL. This timeline should be no different but their Katana is just aimed at different zones
They'll probably look for a casus belli before joining, and also an assurance that Britain won't join on the other side, but I suppose they could make a border incident with Russia, or summat.
Thankee!Just like to say i like the look of this TL.