It's quite possible to find apartments in Tokyo and the surrounding areas for for around 60,000JPY a month. There is absolutely no reason you need to spend over 100,000JPY. My apartment is around 20m^2 and is around 80,000/month. It is a 3 year old, 3 story building (4 apartments) that is a 6 minute walk from two different stations on the Yamanote Line, as well as an equally short walk to a metro line inside the circle. It's only a 4 minute ride to the nearest large station. That places me pretty well in the center of Tokyo proper.

With rent, utilities, food, transportation, and a basic cellphone, I think you should be able to manage alone on 160,000JPY/month if you are smart. Luxury items and amusement would be, of course, extra.

Of course, finding a rich sugar-momma to take care of you every night is on you...

Sincerely,
-Eric

ps-Who can guess where I live?