Shinjuku station: the world's busiest station by far. A place where over 3 million people pass through every single day. A commuter hub where more than 10 different train lines converge. A modern day railway maze where you can easily get lost.
It is also an area where entertainment, shopping, nightlife, and a red-light district fuse into one, creating a complex and buzzing metropolitan city. Thousands of people visit Shinjuku everyday, either for their meals, meeting up with friends, the bars/nightclubs, or tourists passing through to do sightseeing and shopping.
At Nishi-Shinjuku to the west, skyscrapers dominate the skyline business district, which is where the Tokyo Metropolitan Government Building (TMG) lies. Don't forget Omoide Yokocho, which is also known as Memory Lane. There are lots of small places to eat at here selling yakitori, ramen, sushi and soba. The air is filled with an amazing grilled food smell. The shops are really small, and on average most of them can only seat around 10 people or so.
You will see lots of locals and tourist sitting and just waiting for their yakitori to be grilled and served. I’m sure after passing by these lanes, you will definitely want to try out the yakitori skewers including grilled meatballs, chicken skin etc.
Kabukicho is also home to a famous red-light district (of sorts). It is one of Japan's wildest areas, a place where various services are offered to meet every kind of taste. There are bars, nightclubs, restaurants and love hotels around as well! This place is filled with neon lights everywhere that will attract your eyes like a moth attracted to light.
You can also find the famous Robot Restaurant here as well - basically a bunch of scantily clad women dancing and operating robots. They have a huge size robot and it is controllable.
You will be amazed at what these world famous Shinjuku areas look like, a mixture of modernization with the old.