Shinjuku is the capital of Tokyo and is one of the largest cities in Japan. You can not walk around this area even for 1 day.
However, using the bus is very cheap.
You can enjoy the whole of Shinjuku for a short period.
For example, you can see Mt Fuji from the top of the Tokyo metropolitan office 200 meters high(depending on the weather conditions) as well as go to Shrine and Kabukicho (No1 red light district in Japan) You can learn many aspects of Tokyo from a licensed guide as well.
