The Japanese said a lot of things about other Asians being their kin. In reality though it was more like Nazi racism against Slavs, just with a lot more hypocrisy.
Extreme Japanese racism can easily be avoided
Just make the Treaty of Portsmouth much more satisfactory to Japan
(Have the Dogger's Bank incident expand, Britain join the war, and forge a peace treaty that strongly favors Japan, such as huge reparations and the annexation of all Sakhalin.)
This makes the Japanese proud less, because Britain helped them, but they will get a very satisfactory treaty, which means avoiding a violent reaction, and thus sowing the seeds of extremism.
Add also avoiding the Wilson presidency (make Charles Hughes triumph in 1916) and it might mean passing the racial equality clause in the Treaty of Versailles.
Therefore, Western goodwill towards Japan still exists, and therefore Japan does not feel its inferiority complex, and they do not go crazy later.
Besides the survival of the Qing Dynasty, which means neither the era of warlords nor the Mukden Incident, thus Sino-Japanese relations are much better.