Let’s start with the positive points.
The flat is quite spacious for Tokyo’s standard and location is good (close to metro, interesting neighbourhood, a few supermarkets nearby).
Unfortunately, this is not enough to outweigh some serious issues :
1) The cleaningless of the flat is highly questionnable.
Basically, it was only clean superficially. As soon as you touch something, you can see that the flat has not been clean properly for a long time. For instance, the washing machine was so dirty that we had to clean it twice before to wash our clothes. We spent almost two days to make the flat clean enough to be liveable.
2) At beginning, the water heater in the bathroom was not working and we had to take cold shower...
The management company (Matsuri technologies) sent someone to confirm the mal-functioning of the water-heater. After that, they told us that it will probably take a month to fix the machine, and in the meantime we should move to another flat (even worse than our current one). A few days later, another person came to see if it was fixable and it was surprisingly working. All this episode gave us the impression that the management company is not competent at all.
Overall, you get what you pay for. Pretty cheap price for the location and surface, but in a very old building, very poor cleaning and not great customer service in general.
After one week living here, my feeling is that it is better to pay a bit more to get a cleaner flat.