Kaen's place in an ideal location, just a 4-minute walk from Okubo station and convenient for all the sights of Shinjuku, but down a quiet street where there is little to no noise at night. Perfect.
The bed is a semi-double, so could be a little small for two people , but we didn't find it a problem. There's also a futon in the cupboard if you find the bed too small. We've stayed in a few different apartments in Tokyo and the size is typical of the city. If you're new to Tokyo you might find the place small, but it's perfect for two people I think.
The outside space is lovely, perfect for hanging out washing in the sunshine. It's on the ground floor, but secluded by some faux-greenery which is a nice touch. Grab a hot coffee for the nearby vending machine and enjoy in your own private outdoor space.
The map of places to eat nearby, hand-drawn by Kaen was a wonderful touch and we enjoyed a few of her recommendations like cheap and tasty beef bowl. The pocket WiFi was also incredibly useful.