If you are traveling on a budget and arriving in Kansai Airport Osaka late at night, you have to take a note that the last train out of this airport to Osaka area departs around midnight, taxis are available but they are the more expensive option you might have. Sleeping in airport hotel is considered more convenient (for sure), but if you really have a budget constrain, sleeping in the airport area might be the best idea.
As a traveler who sometimes sleep in airport due to some different reasons, I admit that sleeping in Kansai Airport was on my top chart for its convenience and security. There might some places that comfortable enough to stay, but I would love to recommend this area below for you.
It’s conveniently located on the second floor of Terminal 1 Building, between Lawson mini market and the well-known Mc Donalds, and just right in front of the Airport Information Office. There’s a free drinking water fountain in front of toilet behind Lawson store. So you will got your needs of food and beverages supply covered for the night. There’s also a small police station right beside Lawson, so I consider this area is safer than the others.
There are a lot of long benches for you to have a quite proper sleep, with your body fully laid. You can even borrow a blanket from the Airport Information Office right in front of you for free, all you need to do is return it at maximum six in the morning with a big smile and thanks.
And just to add, you need to leave the place at the same time you return the blanket. There will be plenty of public transports heading to Osaka operated already by that time.
Aite then, have a safe and pleasant trip!