I just saw this place on YouTube and I am so in love.
It's a bit far out from Tokyo (its near Yokohama) so I won't be able to go during my trip next week but OMG I WANT TO GOOOO!
It's called Nanjya Monjya Cafe and it is a legit tree house.
You can just hang out in the treehouse, drink coffee, and chill all day!
Plus LOOK AT THESE PANCAKES THEY HAVE.
If this isn't the cafe of my dreams I don't know what is <3
Here's the cafe's website!