Since we arrived at Kansai Airport, we redeemed the metro cards there. Very easy to use, although the metro card doesnt cover all lines. The entrance redemption process was easy for each place, just scan QR. We managed to cover a few attractions, starting at Osaka Castle and ending with Tempozan Park. The Kaiyukan aquarium ticket was a separate ticket, but I suggest going at the same time so you get to cover the transport to tempozan with your metro card. We bought it on the spot to avoid missing the timeslot.