Quite far from the JR Shinjuku station (be aware that the station is a HUGE one). A 5 min walk (if you are on a rush) to Shinjuku Prince Hotel. 30 min brisk walk to the Narita Express boarding area (I know because we did that on our last day). Shinjuku is a strategic place to stay for those going to Mt Fuji and easy access to Narita Express.
More expensive than other airBnB's I've been to but worth it. Looks like a hotel accommodation. Small space but clean. Host responds immediately. Would recommend!