When are you going to Osaka? If you can squeeze out about 5 days, you should try spending 2 or 3 days in Kyoto/Nara. See if you can do the following:
2 Days in Kyoto Nara, go to the major shrines and temple (Kinkaku Ji, Kiyomizudera, Nara Park, Fushimi Inari Shrine etc). 2 Days in Osaka, go to the Umeda building, visit the Dontonbori, Nanba district etc, go to Himeji for a day...
ok, then you will definiintely want a full day and night to cover umeda and dontonbori, the next 2 days you can either go to the aquarium, or shoot over to Kyoto or Sakai to look at ancient tomb (Kofun)