I stayed at Asama's a little over a week, and had an overall good experience! Asama herself is a very kind and accommodating host - I didn't always have time for the breakfast included with the stay, but she went out of her way to make a meal for me when I could, even if it was to-go. She was also very flexible with my check-in/out times, and responded quickly to messages.
Room: A bit small (it is all 1 room w shower/toilet attached) but it is totally private - you have your own entrance + facilities. Just enough space for 1 person. There is a small collapsible desk + stool, but more meant for quick eating, less for sitting to work etc if you might need for extended periods. All very clean.
Location: So it is quite a walk (~15-20 min) from Ikebukuro station if that's what you'll primarily be using. I ended up taking the bus over to the station a decent amount (the stop is just down the street, ~¥200 fare) when it was hot/rainy or I had bags, though it's definitely a doable walk on cooler nights when you're not in a rush.
Misc: As another reviewer also mentioned, the staircase up to the room is quite narrow and steep, and it is open air so be careful when it rains + think ahead if you have bigger bags. There is a washing machine to use for ¥200 + outdoor hanging space. Asama also provided towels but if you are used to big bath towels you may want to bring your own.
Overall I think it is a good place for the price to have your own private space, which can be hard to find in Tokyo (Ikebukuro especially). Thank you!