we spent 5 days at Koichi's place with my wife and daughter.
location is great, a block away from union square.
communication with Koichi was good though we havent met him.
this is a room with a kitchen, toilets and bathroom are shared with other tenants. The place was clean for shared facilities but you have to be aware of it.
One point to notice is that the insulation is not good (an AC unit has been installed so there is a hole in the window only covered by a super thin plastic piece) so you have all the noise from the street, and during cold days you can feel the air directly to the bed.
So I would recommend the place because it's a rather good value for money but not in the winter time and not if you are really sensitive to noise