How to book airfares from Narita to KIX?

When searching in hyperdia, there was options to travel via air, I was just wondering how that works? Can I just purchase the tickets at train stations and get to the airport and jump on the plane? And does the hyperdia time include check in times and everything? Thanks.

I think that Hyperdia tries to incorporate typical transfer times. In case of domestic flights, you should check in by 15 minutes before departure time.

Air tickets can be purchased online or through travel agents:
http://www.japan-guide.com/e/e2365.html

Note also thet Hyperdia lists regular fares for air connections, which are often way more expensive than the discount tickets available. More details:
http://www.japan-guide.com/e/e2364.html