What happened before, during, and after Japan's control of Korea in the Japanese colonial era between 1910 and 1945?

A significant amount of change occurred in that timeframe. Korea gained and lost its independence, was occupied by multiple countries, and became a battlefield in a proxy war; to this day it remains cut in two.
Before:
In 1897, Korea broke from China with the declaration of the Korean Empire. That independence did not last long, because by 1905, Korea was a protectorate of Japan, and in 1910, the country was entirely annexed.
During:
Japanese colonial rule lasted for thirty-five years. While industrialization modernized the country, the growth was only fostered so that Japan could enrich itself and extract resources to wage war. Japanese settlers and corporations gained control of Korean land. Japan forced Koreans to serve them as agricultural workers, soldiers, and sex slaves. Under pressure from their colonial masters, most Koreans changed their names to Japanese names.
After:
In 1945, Japan surrendered to the United States and the Soviet Union. They segmented Korea in a process similar to agreements in Europe where Germany and its capital, Berlin, were divided into East and West. The US and the USSR cut the Korean peninsula in two along the 38th parallel. North Korea was under Soviet occupation, and South Korea was under US occupation. The superpowers exacerbated political divides, which resulted in the Korean War. The civil war lasted from 1950 to 1953 and has yet to formally end with a peace treaty.
For sixty years tensions have been high, but recent interactions between North and South Korea have softened the political environment. A unified team of Koreans from the North and South even competed in the 2018 Winter Olympics. If the trend continues, one day the “Hermit Kingdom” of North Korea may open its borders to the outside world.
http://afe.easia.columbia.edu/main_pop/kpct/kp_koreaimperialism.htm

http://afe.easia.columbia.edu/timelines/korea_timeline.htm