Sino-Japanese relations are the way that China and Japan have interacted with each other over a very long time. China and Japan are both located close to each other and they have had many experiences together throughout history. But sometimes these experiences have not been very happy and both countries have had conflicts and disagreements.
For a long time, China was way bigger and more powerful than Japan. China had a lot of people and resources, while Japan was an island country with limited land and resources. Because of this, Japan looked up to China and tried to learn from its culture and ways of life. This is why there are many examples of Japanese art and buildings that imitate Chinese styles.
But later on, Japan became powerful too. In the late 1800s, Japan started modernizing and becoming more like the powerful Western countries. Japan also started to expand its territory by taking over other countries, just like some Western countries were doing at the time. This made China feel very threatened and upset, and they became very angry with Japan. In fact, China and Japan fought a very big war in the late 1800s and Japan won, which made China even more upset.
After the war, Japan treated China very badly and even invaded and took over parts of China. This made China even more angry and they have not forgotten this even until today. During World War II, Japan did many bad things to China such as killing many people and using them for forced labor. This caused a lot of anger and hatred towards Japan and has left a big scar in the relationship between these two countries.
Even today, things are not perfect between China and Japan. There are still disagreements and tensions, especially when it comes to territorial disputes and Japan's actions during World War II. But both countries have also tried to work together on certain things like trade and culture. It's important for them to work together and find ways to get along, even if they have had a long and complicated history.