BMJ Shinjuku Okubo is in a good location near the train station that doesn't require multiple transfers but still takes a good 8 minute walk. We ventured out every day, and the immediate neighborhood is peaceful a few blocks away from multicultural restaurants (Vietnamese, Halal) and Don Quijote. With the basic amenities (yay slippers) and laundry, the space is larger and slightly more affordable than a hotel. There is no elevator but you can bring your luggage up 3 floors easily.
Self-check in is available after hours although the instructions file stated certain office hours. Communication was okay but sometimes emails weren't initiated or sent with reply all so the check-in instructions only went to my partner who misses details.
Appliances (laundry, humidifier) are all in Japanese with limited instructions so use Gxxgle Translate. We tried to use the bath on the last night but the drain wouldn't plug or we didn't know how to operate the panel. Overall, the stay was comfortable.