Kuniaki's place is a great location, with great access to Shibuya and Shinjuku as well as walking distance from Shimokitazawa. I used to live in the Shimokita area and would highly recommend it to anyone looking to come to Tokyo - it has great cafes/restaurants, thrift shops, theatres and small live music venues.
The apartment was very clean and well-stocked with basic amenities, especially a lot of extra linen/towels. I traveled alone and stayed for just under 3 weeks, so the size was perfect for me, especially compared to the size of apartment you'll generally find in Tokyo. The bed was comfortable as well. The one thing I would suggest is to bring a sleeping mask, because the sun is quite bright in the mornings even with the curtains closed.
I didn't have any problems during my stay, but when I did message Kuniaki he was always very kind and prompt, he even left a personal note in the apartment before my arrival. I would definitely stay here again. Thank you Kuniaki!