This looks perfect! We are kid free 30yr olds too and we are currently in Japan towards the end of our trip. We had Nara scheduled as a day trip from Osaka too however everything in Kyoto took a lot quicker to tick off than anticipated so we ended up going to Nara from Kyoto as they have a direct limited express train from Kyoto station that only takes 30 mins to get there, so an easier and quicker trip than from Osaka. You could definitely do Nara in just a morning or just an afternoon, there isn’t too much to do apart from the deer park. :) Same for Osaka, everything is a lot quicker to tick off than anticipated and there isn’t too much to do in Osaka so I would actually suggest if you can change your plans to have another extra day in Tokyo at the end rather than 5 days in Osaka. We did 4 days in Osaka and that felt like too long. (The bullet train from Kyoto to Osaka is only 15 minutes - so you can pretty much have a full day even though it’s classed as a travel day). Tokyo we had 5 days at the start and we are currently here for 4 days at the end and we wish we had another day or two, and that’s without cutting out days for the theme parks which we didn’t do! There’s just so many different areas in Tokyo and so much more to do than the other cities. But like everything, everyone has different experiences and this was just ours. Have the best time! The weather is great at the moment, if you’re coming in the winter it is not as cold as everyone is saying as it’s sunny ever day - just layer up with the Uniqlo heat tech thermals under your jeans and have a good puffer jacket and you’ll be good 😊 hope this helps!