The location is truly hard to beat for the price, basically next door to Higashi Shinjuku station, where the Oedo and Fukutoshin lines can take you to farther popular locations, or easy walking distance from the lively Shinjuku station area, definitely a convenient pick.
Risa & Kei seem to own several units in the same building - the unit we stayed at is actually their listing #14, which was about 95% identical except there's no mirror over the desk area and the decor (purely superficial) was slightly different. Not a huge deal but just something to keep in mind that the photos may not specifically represent the exact unit you will stay in.
We had some cleanliness concerns: the bedroom area seemed not fully sanitized after the previous guest, there were some items left behind, and the carpet and beds weren't as clean as we'd have liked them to be, but we also spent very little time in the room so I wouldn't say it's a huge deal unless you're very particular about cleanliness. I just wouldn't claim it was "spotless" per se. Bathroom areas were fine.
On checkin we discovered a minor issue with the hot water, and the host was unreachable for a less than satisfactory amount of time, but it did eventually get resolved within 24hrs.