Grapehouse is located around 5-10 mins walk from JR Koenji Station. It's not too far from some crowded area like Shinjuku or Tokyo, since you can go there via Chuo Sobu Line or Chuo Line. The area is quiet during the night, which is great if you're a light sleeper.
Sanae-san (the host) shown great hospitality during check in and stay. She'll greet you at the door, sometimes with her dog, and show you around the place. Amenities are great, everything is super clean, and she'll provide a warm water bottle during winter to put near your pillow so you'll be warmer during the night. Lots of up-to-date brochure around her place that you could use for guidance on places you want to visit.
If you are hungry during the night, the place is close to plenty of convenience store (several store of Family Mart, Lawson, 7-11, and 1 supermarket), as well as several restaurant around (McDonald, sushi, bars, yakiniku, pizza hut, rice bowl, etc).
Overall a really great stay, would definitely recommend, especially for solo female traveller.