The cache is not at the posted coordinates (or else it would be on top of the Osaka Castle!). To find the cache, you need to take a journey that will run you in circles. This journey will take you around the Osaka Loop Line. The final is within Osaka Castle Park.
This is a Wherigo cache, so in order to calculate the location of the final, please download the appropriate cartridge from the Wherigo site.
I found this very nice station-by-station description of the Osaka Loop Line.
Here is the Wikipedia page for the Osaka Look Line in English too.
日本語ウィキペディアページはこちら。
To calculate the location of the final, use the information you collect from all of the stations and the formula below:
N 34 41.(E-S+D) (O-H+N) (K-S+R)
E 135 32.(F-P+J) (R-M+I) (H-A+N+J-F)
PLEASE NOTE: There are only four Osaka Loop Line stations where you can start this journey: Osaka, Kyobashi, Tennoji, and Nishikuji. Also, before you start, you will need to download the Wherigo cartridge, and load it onto your device. The only devices that are supported are Garmin devices with Wherigo capabilities, and Android. One Android app is WhereYouGo. I also found an iPhone app on iTunes but have not tested it.
The Wherigo cartridge was made using the very nice Earwigo software. Thanks to AstroBird for helping find an area of Osakajo-koen that was available for the final placement, and to all the Kansai-GA cachers for the fun times! AHO!