Actually history of terminal hotel at Itami Airport goes way back, terminal hotel at Itami Airport is not recent thing.

Hankyu Hotels has opened Osaka Airport Hotel (大阪エアポートホテル) in 1969, yes, it goes that much way back. The hotel was at the exact same location as current terminal hotel. Hankyu Hotels (current Hankyu Hanshin Daiichi Hotel Groups) has closed Osaka Airport Hotel in 2006. Hankyu Hotels was not interested in investing on interior and infrastructure update on the hotel, reason given as due close proximity of Itami airport to city center of Osaka many people simply chose lodging in the city, shift of international flights to Kansai International Airport resulted in less demand, etc.

The facility remained unoccupied after then, but reopen as a hotel in 2010 as Osaka Kuuko Hotel (大阪空港ホテル, Osaka Airport Hotel) and operating as is till today. It looks like the current Osaka Airport Hotel is not run by a large hotel chains, but looks as operating as an independent hotel but not sure.

Osaka Airport Hotel was the first example in Japan where there was a hotel inside of an airport terminal and only such example in Japan for long time. Second example of an airport terminal hotel in Japan did not come about till JAL Hotels opened Hotel Nikko Kansai Airport at Kansai International Airport in 1994.