What to do in Osaka Bay!
Tempozan Harbor Village
This area of the bay is extremely popular for locals and tourists. There are many things to do here, see the market place, aquarium, culture museum, Legoland, a ferris wheel to see the bay area, or take a tourist boat tour. Near here is also Universal Studios.
Naniwa Kuishinbo Yokocho
Inside the mall area contains a food amusement park. The days you can enter the small park depends on the month or season. So look it up before you go. Inside the amusement park contains 20 or so small restaurants which are representative of food in Osaka. The park is centered around a 1960s Japan theme.
Osaka Aquarium Kaiyukan
This place contains different exhibits and offers night visits geared towards couples. Depending on the age, tickets cost anywhere from $0-23.
Universal Studios Japan
If you like Universal Studios, try Universal Studios in Japan. It is a bit smaller than the one in LA but it functions the same. There are some difference compared to the ones in the US though like Super Nintendo World inside the park.