This hotel ranks #1 for the smallest hotel room I have ever stayed in. We stayed on the women's 14th floor in a twin/double room. The hotel photos of the rooms are very deceiving because the furniture is actually smaller than normal. Although we appreciated having a fridge, a tv, a kettle, and some hooks and hanger we struggled not having enough space for our suitcases, toiletries, and food items. The room featured a Japanese unit bath - something I enjoy experiencing - however, the bathroom was elevated and stepping around inside of it sounded like a drum. The bathtub was deep, but very short and hard to climb into as a shorter person. The window was small but had a large ledge for which we could store some of our items. Our room was south facing and would get extremely hot during the day and the air-conditioning only allows you to adjust very little. There is also a very strict cleaning rule in the hotel - they must clean every few days for which you need to be out of your room for a large portion of the day. We got sent a couple 'notices' under our door as if we were breaking some law for not wanting our room cleaned, lol. We joked that we were about to be fined for being disgusting, lol.
The pluses of booking this hotel is the price (by comparison to everything else), it's proximity to Shinjuku Station, and it's relative quietness with plenty food and convenience options located inside and around the hotel. Inside the hotel are 2 convenience stores: Family Mart and Lawsons. If you need a snack or drink you do not need to go to far. There are 6 elevators and although there would be the occasional wait, it was never longer than a couple minutes. There is laundry onsite with a coin exchange machine (only accepts JPY 1000 bills), though it is a bit small and therefore busy and slightly more expensive. There are a few restaurants on site including a fishing restaurant (!). There is also a karaoke bar in the basement, but it seemed pretty dead inside. If you need extra toiletries the hotel provides some free of charge in the lobby area.
I would say skip the Cafe & Bar Baron, their breakfast buffet is overpriced at JPY 2100 and pretty disgusting (unthawed fruit, scrambled eggs were soup, and just generally not tasty). One of the restaurants was closed for some reason during our stay, but we did try the Italian restaurant which was pretty good.
The three lowest floors of the hotel are like a mall and are comprised of the hotel lobby, restaurants, the convenience stores, and a few other services, but it has a pretty empty vibe to it. We may have also joked that it reminded us of a local dead mall from our home city.
If you are looking for a cheap and somewhat quiet hotel in the middle of the Shinjuku universe then this is your place, but keep in mind that you will be living in a hot closet! Good for a couple nights stay, but perhaps not for 5 or 6 nights like we did.