Very nice, clean and comfortable place, really big enough space for a big group. We were 12 people spread across 4 rooms. Functional kitchen and dining area. 2 toilets but only 1 bathroom. So just schedule your shower time slots for those with big groups. All household and bath essentials provided, and there's free WIFI!
Might be a challenge for those with big bags as the stairs were narrow and steep. Suggest those with more or bigger luggage to stay on the ground floor.
Location is on a safe and quiet neighborhood. The place is right on the street (but not a busy one), with a 24h supermarket right across. A few minutes walk (800m) to either the higashi-nakano JR station or the nakano-sakaue metro station. We were a big family with 2 seniors and 4 kids, and the walk was bearable (also bec weather was cool).
Communication with river was fast and efficient.