I had a very good stay at Masaki and Haruko's place! It's a nice, quite neighborhood but really near Tabata station and Yamanote Line. And there are several Convenience stores and supermarkets in the area. The apartment was very clean and had everything i needed. There were several explanations for everything in english for me. The pocket wifi was definitly one of the best things for exploring Tokyo.
Masaki and Haruko replyed to every message very fast and told me some good recommendations.
I stayed for 2 weeks and had a great time! Thanks again!