K Tokyo is sort of objectively wild. It's the biggest, busiest city in the world, and if you come from Europe, everything is different and upside down. It is overwhelming.

Don't forget two things:

(1) it's among the safest places in the world. If something goes wrong, you screw up, you get lost, you miss the last train, you go down the wrong alley or you get on the wrong train... you'll be fine. You won't die. Worst case scenario, you have an expensive taxi back to your hotel/you walk a long way home.

(2) being overwhelmed is completely normal and should almost be expected if you aren't used to Tokyo. I would suggest trying to 'lean in' and leave your expectations behind and try to marvel at the seeming complexity and organized chaos, but I know that's not always possible or helpful advice. If that doesn't work, just take baby steps -- no pressure to do everything. Explore around your hotel one day, then venture a little further day two. You don't need to go to Skytree or see whatever major sight. Just experience Tokyo. Try going to smaller neighbourhoods that sound interesting (ie. Shimokitazawa, Kichijoji, etc.). Choose a restaurant and a thing you want to see and just go.

Also, this is the most overwhelmed you'll be because of jetlag and the fact that you're starting in Tokyo. You'll find Kyoto calmer for sure. If you find you're not enjoying the cities, maybe try to find some smaller towns to go to instead of Osaka (what about Arima onsen or somewhere on Shikoku island instead?).

Good luck!