For citizens, how do professors work hard is not well known. Generally speaking, it seems that professors are deemed having too much time in the US. This article below describes the counter generals statement of easygoing professors.
The Atlantic: How Hard Do Professors Actually Work?
Actually, some professor does work very hard. In this article, Philip Guo says that he works more than 60 hours in a week. The content of his work is spread from teaching students to writing academic papers.
The situation is also similar in Japan. But there are some unique characters in professors in Japan.
First, since the budget for education is limited compared to other developed countries, professors are struggling for keeping the time to teach students. We have to get grants for continuing research. And Japanese universities and sponsors do not evaluate the achievement of education. It is an irony that the more eager to teach students, the less they are admitted by the director in Japan.
Second, there are many post-doctoral researchers who are suffering from the lack of stable posts. It is the same in the US, but in Japan, they have to deal with several tasks in a university as a temporal lecturer.
There are differences, however, in the situation among the academic departments. Medical doctors are relatively fortunate in gaining an academic post, compared to other medical staffs such as psychologists. Instead, many of them are extremely busy. Japanese professors of medicine are usually engaged in both clinical work and research, as well as education for medical students.
Anyway, academic posts are shrinking despite increasing persons with a doctorial degree. It is a global tendency. I do not think it is miserable, though. It is simply preferable that many researchers are growing.