Shinjuku is one of the bigger inner-cities in Tokyo. Just to get an idea of how big the Shinjuku ward is, it houses 13 million people, more than the entire population of Sweden. Very touristic spot, and for good reason. One of the most famous spots is Kabukicho, that is actually a red-light districts. That is not to say that it is entirely non-family friendly. The red-light part is quite hidden by the naked eye. You will find quite a lot of tourist families walking around the area. However, it has it’s darker alleys away from the main streets. That is not to say that it is an unsafe area, if you keep by the more popular areas in Kabukicho, you won’t feel unsafe. Remember, we are still in Japan where “dangerous neighborhood” quite a different meaning to other western areas.
By the best of my knowledge, I would divide Shinjuku into a few different parts. I would say that we have Kabukicho, the business district, the massive Shinjuku Gyoen National Garden, Korea town and Shinjuku Ni-chome, also known as the gay district.
The first thing that you will experience when you arrive at Shinjuku is Shinjuku station, which in itself could be considered a touristic spot, or rather a dungeon if you may. It is the world’s busiest transport hub by far, used by an average of 3.5 million people per day (2018). The station has well over 200 exists. You could imagine how easy it would be to get lost, and how difficult it might be to find the right exit, if you can even find an exit. That being said, it is not impossible. I have a little bit of information and hopefully helpful tips on how you should navigate in these massive train stations [link]. Recently, they have improved the Shinjuku train station, and finding the way out has been massively improved, hopefully that helps you.
I would recommend to first do two things in Shinjuku. If you are there during the day, you should head to the Metropolitan Government Building and/or Shinjuku Gyoen National Garden. If you are there during the night, you should go to Kabukicho. I will go further into detail regarding this.