We had a very bad experience for our 1 night stay with 2 rooms at the end of the ground floor. There's bad smell from drainage but nothing can be done to fix it. As per hotel staff, they are full house, however they can't arrange any air purifier or any solution. In a small room, we have difficulty to sleep with such bad smell with kids. The final suggestion from hotel staff is open the window a bit, while it's around 5 degree outside and the window is facing their machinery corner.
Another thing is how their toilet and shower corner being equipped. No matter how small is bathroom in Japan cities, that's the most squeezed one, can hardly sit down to utilize it.