Kita-Shinjuku is in the heart of Tokyo, yet most parts of this area have a peaceful touch to them.
Here you will find the famous Korean town, (shin Okubo station) Takadanobaba, and links up to Waseda University. Very convenient area to get around all over Tokyo. The ideal place to live for students as well as full-time workers. There is plenty of Language schools around such as ISI Japanese Language School and Coto, further down in Okubo and Shin-Okubo we find the Kai Japanese Language School.
In the Okubo area, you can enjoy nightlife and good-tasting Korean food. from there it's  Just a 10 min walk to Jr Shinjuku station where you have plenty of more entertainment such as bars, restaurants, karaoke, game centers, cafes, and much more. Alongside Kanda River close to Takadanobaba you can enjoy a day and night stroll with a beautiful view, especially during the cherry blossoms season.
Kita Shinjuku is a convenient area with good links to major hubs but also has more quiet areas to relax from the fast-paced city life.