Mitsuko's place is lovely and clean and close to public transport. The location is really good: 5-7 mins walk to metro (Keio New Line, 2 stops from Shinjuku) or bus (#66, 20 mins to Shibuya). You have a few shops and food places close by.
The apartment is very clean and as depicted on the photos. It's just spacious enough for 1 or max 2 people, so this is for you if you're planning to use this mostly for sleeping. The bathroom is really small; I'm 6'4" and just about managed.
Other than that it's great for a few nights in Tokyo! Mitsuko provide detailed instructions and communication was great! Also the portable wi-fi router (free for your stay) is convenient! Would stay again!