Shinjuku-ku is a west-side ward built around access, with room to adjust once you look past the station. The Yamanote and Chuo lines are the starting point for comparing big terminals, the Marunouchi Line keeps Nishi-shinjuku, Yotsuya, and Otemachi-side office routes open, and the Toei and Tozai lines are useful for comparing Kagurazaka, Ichigaya, Takadanobaba, and Ochiai. Nishi-shinjuku, Kagurazaka, Yotsuya, Takadanobaba, Shin-Okubo, and Ochiai are different searches, not one single Shinjuku search.
It helps to separate the nightlife core from the street you will actually walk home on, since Shinjuku is a street-level decision — Kagurazaka, Yotsuya, and Ochiai can feel closer to calm central Tokyo than to station-front Shinjuku, while Takadanobaba and Shin-Okubo keep the access but trade it for more street energy and noise. Use Shinjuku for access, but choose the actual area for daily life, comparing Kagurazaka, Yotsuya, Ochiai, Nakano, Bunkyo, and Toshima early if the station-front image feels too loud or expensive.