Shinjuku is the most crowded area in Tokyo partly because the convenient access. There are always tons of tourists, business people, and students. There are so many places and shops to go, but here I introduce five.
Kabuki-cho has a lot of restaurants and places to eat and drink. Also there are many girls' bars and such kinds of things. It's always very bright there even at night because of the lights of the stores. You might not so safe in Kabuki-cho because there are always too many people.
#2 Shinjuku Gyoen
If you get tired from those crowds, Shinjuku Gyoen is the place to go. It's a huge garden which has not only Japanese style gardens but also British and French ones. There's a restaurant inside that serves healthy and delicious Japanese food.
#3 Tokyo Metropolitan Government Building
Tokyo Metropolitan Government Building is one of the most iconic building in Shinjuku. You can go up to the observatory for free. From there, you can see the whole view of the city of Tokyo. It's stunning, especially at night.
#4 Shinjuku Golden Gai
Shinjuku Golden Gai is a small area of Shinjuku, Tokyo, Japan, famous both as an area of architectural interest and for its nightlife. Over 200 tiny shanty-style bars, clubs and eateries are squeezed into this area. In this area, shooting photograph and video on the street is prohibited. The tastes of each place is quite unique.
#5 Shinjuku Isentan
Shinjuku Isetan is probably the most famous department store in Japan. It has more than 80 years history. They sell a wide variety of goods from clothes to food. But their appealing point is fashion. Everything they sell is fancy elegant, and pretty. If you like shopping, you should visit Isetan even if you don't want to buy anything.