Also book tickets for the Bullet Train now
really? we could buy bullet train tickets at the station just fine. Was also there during christmas a few years ago, but it might've been changed.
For every other stuff: Absolutely yes. Search special events, museums, etc. and book early. We didn't knew that and had several sad moments, where we were used to museums in our country (just go there) and were disappointed. Bad research on our side.
Tokyo was for us just amazing to just wander through and explore. what a city! Just research some districts and choose some to explore. For me higlights were Shinjuku + Shibuya for obvious reasons (loved especially the little bars in Golden Gai) , Shimokitazawa for the thrift shops (sooo many, and with a lot of choices for men - Japanese men are way more fashionable than Germans lol), Akihabara for the nerd shops.
I also like to wander in the less touristic areas more outside to get a feel for the living when I am traveling. Less specific tips here for Tokyo, but definitely worth doing, there are some really nice laid back districts. I also like to go over university campus and the Tokyo ones are quite interesting.
In Osaka you need to eat as much as possible.
I can also highly recommend to do a daytrip to Hiroshima. From Osaka its like 1,20 hour with the bullet train (over 200 miles lol, I love these trains). Super interesting to see the remnants of the nuclear bomb, the peace park and museum and so on. And it gave me hope too. To see a city basically getting annihilated and nowadays thriving again says something about human resiliance.
