Twin Room in the next building has a nicer design and more spacious and comfortable than the single room. It was noisy when I stayed in the single room, every morning there would be a staff pushing a trolley :( I would choose this hotel if I ever need a twin room in Tokyo. The hotel is just opposite Oimachi station where Rinkai line and Keihin-Tohoku line run, so location wise it is perfect to access Shibuya, Shinjuku and other places like Ginza only require one transfer. The neighbourhood is quieter and less crazy/noisy compared to touristy places. There are restaurants, Starbucks, Mac, Hankyu supermarket and Atre shopping mall, where you can buy snacks and essentials. You can find Loft (small store), Muji and Uniqlo here.
The Haneda airport limousine stops just outside the hotel - very easy. To access Narita airport, you will need to take the train to Shinagawa (1 stop) and transfer to Narita Express. Or you can also opt for a much cheaper option - take train to Tokyo station (a few stops) and airport bus at Yaesu South exit. Airport buses are frequent and you can buy tickets on the spot. It costs 1500 yen one way. Do note the airport bus allows one bag and one check in sized suitcase only. If you are travelling outside of Tokyo and do not want to take your extra luggage, the hotel allows you to leave the luggage in their cloakroom for 300 yen per night - very affordable. The man made onsen is public, not exclusive to the hotel guests. It costs 500 yen per entry.