Actually the study of China in Japan was highly regarded until the 1800s. Elites in Japan were well versed in Chinese culture, such as Confucianism, literature, history, etc., and many would have been bilingual. They understood that China was massively larger and more powerful than Japan for all of recorded history, and would continue to be so in the foreseeable future.
The initial turning point came with the Opium Wars, when China was decisively defeated by a much smaller, yet highly advanced British expeditionary force. As a consequence, China was forced to give up many of its legal and trade rights to various European states, starting what is known in China as the "Century of Humiliation."
China's defeat also came as a shock to many Japanese, as they had regarded China as the premier world power. So when the United States ended Japan's isolationist period in 1853, the elites believed that they needed to emulate the West instead of China. In their minds, Japan had to become a colonial power like Europe, or else they would be torn apart like China. The West represented progress and power, while China represented stagnation and defeat. After the Meiji Restoration in 1868, Japan embarked on a period of rapid industrialization and militarization in order to put them on par with the European states.
The final nail in the coffin of Japan-China relations came in 1894-5, when Japan defeated China in the First Sino-Japanese War. Japan gained control over Taiwan and received similar privileges that Europeans enjoyed in China. The war upended what had been the de facto pecking order in East Asia, placing Japan as the leading power in East Asia.
You are welcome.