Tucked away in the 6th floor of the Eiwa • 永和 Building (Kitahama, Osaka) is a nice little gallery of contemporary art called Sai Gallery. Around Nakanoshima (Kitahama, Tennma) there are a great many galleries, and plenty to see. Though Sai Gallery is a little hard to find, it's worth the visit if you happen to be in the area.
Sai Gallery is run by Yoko Nishimoto, and has been around since 1991.
Unlike most small Galleries, it has a counter with chairs against the window on the river side, so you can sit and soak up a very nice view of Nakanoshima after browsing the current exhibition.
You can check out more information on their website: