Since you know you will be riding the Haruka round trip in a 3 day period, you can save a lot by purchasing the 3-day JR-West Kansai Area Rail Pass either before leaving or upon arrival at KIX. The cost is much less than the Haruka round trip and you can use the Pass for any other local JR trains during the 3 days. Unlike the Unlimited Rail Pass, the Kansai Area Pass can be purchased in Japan for 5,000 yen. I just used mine to get to Nara today after arriving at KIX.