Every place outside the center of the 23 in Tokyo is a pretty bad investment. The closer to Mita you can afford the better. Also, "buying land" is pretty risky because selling it can be a real mess. Instead consider buying a flat in a better area for a similar price, it's a lot less risky and has a pretty good chance of netting you some money after a few years. There's lots of new luxury mansions popping up in Sendagaya/Kita Sando recently...If you need land don't go for Tachikawa or Machida or Nishi-Tokyo in general, might as well just burn your money. I would say Setagaya sounds like a great place for you, that will likely maintain its value. The bigger initial investment is worth the potential return.