Josh is by far the most amazing host I've ever had. I've stayed in more than 10 Airbnb's and he is actually the first host I have ever met in person. He went out of his way to make a reservation for us at Sushi Iwa (Michelin star sushi) a month in advance of our stay at his Airbnb. He even loaned us his vacuum and gave us more toilet paper while at it! His communication is great and he replies within an hour.
As for the space, it is small but I would say would be good enough for 4 people. The walls are thin so you can hear conversations from the people next door (also another Airbnb I believe). The train station is loud but I did not mind it since it really puts you in the feel for staying in Japan. It is about a 3 min walk to the station and a Lawson's. Shinagawa station is about a 5 min train ride if you take the airport line or a 12 min train ride if you take the local line, which is a huge benefit for exploring Tokyo and Kanagawa.
I would definitely stay here again!