Where in Shinjuku will you be staying?
I forgot the name, but I frequented this place often when I was staying in Shinjuku:
shinjuku sunflower tokyo - Google Maps
Don't remember what floor it was on or if Sunflower was even the name of the place or the building. But I remember it having nice food, good beer, open late and close to my hotel. Probably went there almost every single night for a nightcap.