We are a family of six (including two elderly) and we booked the 2F + 4F apartments.
First and foremost, Dai was really prompt in his response and very very amiable. He really went above and beyond to ensure our stay was comfortable!
By Japan's standard, the apartments are really spacious and definitely good for four pax per apartment.
The apartments are indeed clean. I have a rather sensitive skin against dust and they showed no negative reaction to the bed linen.
The water pressure in the shower room is very good.
The wifi that was provided works very well (speed was faster than the one we rented from our home country) and could last for approximately 10 hours.
Toilet is situated outside of the apartment (as per the floor plan provided by the host). On our first day, my granny did feel a little uncomfortable with the toilet out of the house but she eventually got used to it. Not a major issue since Japan is a relatively safe country.
The nearest station is JR Ryogoku station, therefore very convenient for travellers with the JR Pass. For those using metro subway pass, there are two stations nearby - Higashi-Nihombashi (10 minutes walk) & Ryogoku (15 minutes walk). However, they are located quite a distance away. I have my grandparents with me and we had to take taxis home on some nights especially since it's winter. Not a problem since the short taxi ride cost approximately 570~650 JPY only. Also, Higashi-Nihombashi station provides direct access to both Narita and Haneda Airport. You will save quite a bit as compared to taking the Keisei Skyliner and Narita Express! :)
The only negative issue I had was regarding the hot water supply. There is a control panel for the hot water system in the house. There was one night where the hot water ran out while I was in the middle of a shower. It was already 1am when I texted the host for assistance, and Dai woke up to guide me in adjusting the settings for the hot water. Unfortunately, the hot water took quite a while (I tried waiting for half an hour but eventually gave up, so I am unsure how long it took). I had to shower in icy cold water on a winter night. Dai got in touch with the company for the hot water system the next morning and I believe he now has a better understanding of the control panel.
All in all, I would highly recommend Toshi/Dai's apartments to everyone especially extended families travelling together but prefers staying in separate rooms. I will definitely not hesitate to stay with them again in future! :)