I stayed here for nearly two months, and the experience was so wonderful! I could write very long paragraphs, but to save your time, here is an abbreviated list:
1. Check in was very smooth. Manami was very responsible to airbnb messages and very flexible on check in time.
2. During my stay, Manami would visit once every week or so to change the bed sheets when I was out of the house.
3. My fiance came over for the last week, and she offered to change the bed from double to queen size. The bed is pretty comfy.
4. We travelled for another week out of Tokyo, and Manami was kind enough to allow us to leave our luggages at her place.
5. Koenji is so convenient and affordable. You can wake up at any time of day and walk a few minutes to convenient store or restaurants. For the two months I stayed here, it seems pretty safe any time of day. (Trust me, I walked outside in all hours)

To make this review fair, only one thing to note: the ladder to the loft is pretty sturdy, but since the loft is low, you do have to be careful. Not recommended for large and/or elderly people, but can be fun when you get used to it.