If you got a job in those places (little hong kong is more like a themed mall then it is a town like chinatown in Yokohama) yes you would have to commute.
But there are many Chinese restaurants spread throught tokyo in many areas, not all the chinese restaurants in Japan are in Chinatown. If you speak Japanese enough then you could probably get a job in a convenience store, I knew many Chinese who worked in them.
But again, the job market is very tough now, so many Japanese people are going for any job they can get as well, so you're up with a lot of other competition.
Wish you the best of luck, Its hard for everyone now.