The guide to find Masami's apartment is very detailed and accurate. 2 stops from Shinjuku.
The apartment is cosy and neat. There are 2 twin xl sized beds and a queen(?) sized bed.
About 20min to reach meiji jingu, ~15 min to reach the metropolitan government building (there are 2 observatories at 45th floor).
There are very nice restaurants on the way to the subway, the ramens are very high quality and delicious.
About the small portable wifi device, the battery lasts roughly 8.5hrs at full charge. It automatically connects to the internet in the apartment, subway and malls, so it's very easy to find the way around the Tokyo using Google maps. The device states a data cap but throughout the trip with a lot of usage it still shows 0gb used.
About the washing machine, it finishes its job about 45min and there is a clothes dryer in the bathroom, pretty high-tech.
Didn't meet the host throughout my stay but she replies to my emails quickly and she has been very patient and helpful.
I will definitely stay at Masami's apartment again.