The loaction is unbeatable, we literally just used the room for 6 hours before an international flight to give my 2year old son a sleep. It was perfect.

I have no idea why you would stay here if not just for a flight connection. We will use it again and again.

I stayed here twice this year and found this hotel to perfectly provide all I expect from an airport-hotel. It's very easily reached from the railway-station and terminals, check-in and check-out very smoothly, the room is large, clean and well appointed, there is a 24-hour convenience store and a food-arcade in the same building and more shops and restaurants in the terminal building just 2 minutes walk away.
I was able to book a room for 10.000 Yen both times via the internet. Breakfast wasn't included and I chose to have it at the terminal building as the hotel's seemed a bit expensive.

The sheer convenience of the location means I regularly stay here before an early flight out. I have always found the staff to be great - polite, helpful, and efficient.
It is somewhat disappointing to have to pay extra to use the pool and sauna, and indeed for internet access.
If you ask, you can get a room from which you can see the planes coming in.

The Nikko Kansai has an unbeatable location -- located right on the premises of the Osaka Kansai airport. No shuttles to catch, no extra buses or trains. Just a three minute walk connects you to the terminal, which is full of shops and a 24-hour convenience store in case you need to buy last-minute gifts for family and friends or get something to eat and drink.

The design of the hotel itself is a little odd, with the check-in room on the first floor and the connection to the terminal on the second floor. So if you are flying domestically within Japan and land on the 2nd floor you have to take an elevator to the first floor. A small inconvenience but somewhat awkward.

Those of you who fly in from overseas will exit the airport terminal on the first floor of the terminal, but you will need to cross the street to make it to the check-in.

The rate I was able to book was a little expensive, but the room was large, even for a semi-double. Water pressure was a little weak, but perhaps that's an inevitable consequence of being on a manmade island. Large bathtub and the usual range of amenities made for an above-average room, but Internet here costs extra and the rooms look like they have not been renovated or updated since the hotel opened ten years ago.

Within the hotel grounds, there are a few restaurants on the third floor of the hotel, a delicious tonkatsu pork cutlet restaurant and a 24-hour beef bowl restaurant serving cheap but filling fare at about 400 yen ($3.50). For those of you on a budget, I recommend the 24-hour restaurant or a midnight run to the convenience store on the airport grounds.

The hotel also provides free newspapers, although I'm not sure if they also provide English newspapers on request.

If you are pressed for time and would like a relaxing night before a long overseas trip departing from Osaka Kansai early in the morning, I recommend you consider this hotel. If your flight leaves in the afternoon, though, you might also consider the less conveniently located, though more affordable, hotels reachable by free shuttle bus from the airport.