Right now if you want to go from Tokyo to Minamisenju by train, all your options would require you to change trains at least once.
If you prefer JR, you can take Yamanote/Keihin-Tohoku lines but you will need to switch to Joban line at either Ueno or Nippori stations. If you prefer the Metro, you can walk to Otemachi to take the Tozai line but you will need to switch to Hibiya line at Kayabacho station.
Well here’s the good news — come 2014, Joban line will be extended all the way to Tokyo station so you can say goodbye to train transfers.
Expect apartment prices to go up in Minamisenju real soon. 🙂