Personally I would give Kansai a miss and head to Itami.
Since Kansai's second runway opened far fewer aircraft approach past the sky hall.
Still ok but not what it used to be.
A few short train rides and your at THE best photography location in the world bar none.
Designed for photographers a multi deck park mid point beside Itami's runway 32L with cover monitors for arrivals and departures and shops it is incredible.
Kansai is a poor second place to Itami, very poor..