Visa: got invitation from someone I know who is a resident. Process takes max one week. And almost never gets rejected for tourists. I went myself in mumbai to the consulate and got it done.
Duration: 1 month. I had place to stay in osaka so that was free. But in tokyo had to book a hotel.
Expenses. Close to 1L for the month. Again this is because 3 weeks free stay. But spent a lot on shopping because everything was too cheap when I went.
Itinerary: went to nara, kyoto, via osaka. Back and forth. Spent a day in nara, and kyoto. Covered main places only. In osaka, went to cup ramen museum. Usj, dotonbouri, mozu, osaka castle and bruno mars concert☺️. Tokyo went to teamLabs, ghibli studio. Yokohama via Tokyo, gundam factory, ramen museum. You can also do mario kart and other touristy stuff from yt. Also, definitely try attending a concert in japan. It is so good. It is very organised and you’ll be amazed!
PS: I have been to japan twice with family so visted a few places again and some new.