Yes, Tokyo is a 24-hour city. While not all businesses and attractions are open 24/7, there is always something going on in Tokyo at any given hour. Many restaurants, especially in busy districts like Shinjuku, Shibuya, and Roppongi, stay open until the early hours of the morning, as do numerous karaoke places and bars.
The district of Shinjuku is particularly known for its nightlife, featuring areas like Kabukicho (an entertainment and red-light district) and Golden Gai, which are busy well into the night.
Konbini like 7-Eleven, Lawson, and FamilyMart are open 24 hours a day. Some of the larger Don Quijote discount stores, offering everything from groceries to electronics and clothing, are also open 24 hours.
In addition, Tokyo is home to multiple 24-hour internet and manga cafes, where customers can read manga, use computers, and even sleep on couches or in private booths overnight.
Public transportation, however, does not run 24/7. Trains and buses generally start around 5 AM and stop around midnight or 1 AM, depending on the line. Taxis and ride shares are available during these hours, but please note that taxi rates increase late at night.