Chinese people in Japan are not a monolithic group of people but a diverse kind. The mainlander, Taiwanese, Hongkongese, and Macanese populations combined together surpass the number of Koreans in Japan, so you could almost say they are the largest non-Japanese ethnicity in Japan.
Old Chinese immigrants to Japan are pretty well-settled today. Unlike Koreans, they have less issue adopting Japanese style names, which allows them to go into professions such as medicine and do well.
A large number of (mainland) Chinese students studying in Japan take up part time work in the food industry. It's rare today to walk into a restaurant in Japan and not be served by a Chinese waiter. It's really up to themselves whether they remain in Japan for a career afterward or if they return to the mainland when they're done with school.
There exists sweatshop conditions with workers brought over from the mainland under the trainee visa. The pretext is that they are trainees at factories in Japan of multinational manufactures. They can't leave the factory without losing their visa and facing deportation, so they put up with it.
The Chinese mafia had a strong presence in places like Shijuku Kabukicho, but they're not counted in the statistics.
There are more Korean illegal aliens than Chinese in Japan, despite there being more ethnic Chinese there. That suggests the Chinese play by the rules somewhat better than Koreans.