On May 8, two China Coast Guard (CCG) ships intruded into the territorial waters of the Senkaku Islands and pursued a Japanese fishing boat that was operating in the area. Several Japan Coast Guard (JCG) ships patrolling nearby warned the CCG ships, and took steps to protect the fishing boat that reportedly led to a tense face-off. The CCG ships remained near the fishing boat within the territorial waters, not leaving until May 10.
The Japanese government immediately lodged a protest, pointing out that the incursion into territorial waters was an infringement of the nation's sovereignty. Beijing responded that the CCG ships were simply regulating the illegal operations by the Japanese fishing boat in Chinese territorial waters, and demanded that the JCG refrain from obstruction in the future.
What prompted Beijing to do this? The general observation would be that China took advantage of Japan dealing with the rising COVID-19 infections, by stepping up its offensive against the Senkaku Islands, which Beijing claims as Chinese territory. Alternatively, we could analyze it as the Xi Jinping administration adopting a more hardline stance on Japan as a diversion at a time of growing domestic dissatisfaction while the COVID-19 pandemic slows the Chinese economy. Based on available objective information, however, it appears likely that this incident was the result of a CCG policy of cracking down on foreign fishing vessels in East Asia generally.