I was privileged to stay in Manami's apartment for several weeks and it was simply amazing. Manami and her family were so friendly and hospitable. Manami's father picked me up at Koenji Station even though I was late and couldn't communicate that fact, and he even kindly made time to drive me to the station on my departure even though he was busy. I had some small trouble with the wireless internet which was 100% my own fault, but still Manami and her parents were so quick to call the service provider and did everything they could to help.
The apartment is clean and feels very homely. It has a great charm and living in it was a great experience. Manami and her family paid attention to so many details, as others have mentioned, that even if one forgets to pack some things, it will most likely be provided. So I could immediately settle down after a long and exhausting voyage. The area around the apartment is pretty quiet for Tokyo I would say, so it's no problem to relax after a busy day in Tokyo. As for comments regarding the apartment being small, I would disagree. It is definitely spacious enough to feel comfortable and not feel cramped, especially after having seen some of my friends' apartments in Tokyo.
Koenji itself is also a very charming place. It's not as busy as the more famous areas in Tokyo but that doesn't mean that there's nothing to do. On the contrary, there are many convenience stores close by (the closest to the apartment is only maybe 20-30 meters away), reasonably priced good quality restaurants and other food places, bars and some very unique shops. It's worth planning at least one day for exploring Koenji I would say.
It is also a great location for reaching the famous Tokyo areas since the huge station of Shinjuku is only a few minutes away by train and from there it's very easy to reach almost any place in Tokyo.
Again I'd like to thank Manami and family for being able to stay at their apartment. It made my time in Tokyo so much more enjoyable. I very much hope to be able to visit again!