https://www.japan-guide.com/e/e2420.html
"Japan has three, relatively large Chinatowns (中華街, Chūkagai): one in Yokohama, one in Nagasaki and one in Kobe. All of them originated as residential areas of Chinese merchants, who settled around the ports that were first opened to foreign trade after the end of Japan's era of seclusion in the late 1800s or earlier.
Today, Japan's Chinatowns are tourist spots and dining destinations, popular for their restaurants and "exotic" atmosphere, rather than residential areas of Chinese immigrants, although Yokohama's Chinatown, for example, is still home to several thousand residents of Chinese descent."
https://en.wikipedia.org/wiki/Yokohama_Chinatown
"Yokohama Chinatown is the largest Chinatown in Japan (larger than Chinatowns in both Kobe and Nagasaki) and it is one of the largest in the world.[citation needed] There are roughly 250 Chinese-owned or themed shops and restaurants scattered throughout the district, with the highest concentration centered on a 300 m2 (3,200 sq ft) area."
Osaka has a Koreatown too: https://insideosaka.com/korea-town-tsuruhashi/
I doubt an actual Italian neighborhood, but in Tokyo years ago I found an indoor mall made up to look like an Italian village.