Tokyo is a vast city, but the good news is that most neighbourhoods are actually very walkable. Many attractions are spread out across different districts, and relying solely on walking could be time-consuming and exhausting, not to mention impractical. Tokyo has an extensive public transport infrastructure that will take you to your desired district.
Combining walking with public transportation is the best way to explore and enjoy Tokyo. And just to give you an idea, I walked over 20 km every day in Tokyo on my last visit there. When you do decide to walk in Tokyo, it's great, safe, and comfortable.
There are dedicated pedestrian areas, motorists are respectful of pedestrians at all times. Even walking next to the main road is a fairly relaxing affair, as the pedestrian side walks are very large to accommodate people and bikes too.