how do historians get a veiw of a historic person?

I usually work in Clinical Anatomy where we can use biomechanics to provide some tests but I am currently trying to find information on a historic person named Itosu. There are books written about his profession, the time period he lived and the events that occurred in his life. There is very little that is concrete and even the information that seems to exist seems to give various meanings. I came across something that said he worked in a middle school and college. when I dug more about the times, there was a book that said elementary school was 8 years and middle school would be the next 5 which. This would seem to point out that "middle school" was actually high school. Sorry for the rant the question is how do historians do research on a person? Do they look at the events around their lives to see what was happening?