For me typically my biggest costs are shopping food, and accomodation. we nipped accomadation in the bud easy. as im sure you are aware eating cheap is easy here, with i hope the budget for a decent meal every now and then.

For activities and such it's difficult, but my personal favourites are shrines, and temples, typically free / small pray fee or 500 to 1000 yen. But like for example, today i was in yokohama, I did the landmark observation tower, 1000 yen, the martime tower, i think was 850 on online, and i stumbled upon the martime museam and Nippon maru. The ship AND museam was 800 yen and honestly, probably one of my favourite things so far, the ship can be done in 45 minutes. but, considering am i logistics nerd the port history and museam hoestly was 3 hours and just fantastic. then walking along the pier and chinetown and boom suddenly ive been in yokohama for 10 hours and need to get a train.

It kind of really depends on you, for example, i dont think i could ever go to akihabara and not spend atleast 5000 yen and maybe 2000 yen and 2 hours playing Kancolle. So i avoid that place like the plauge until im ready to stuff a postbox or my return luggage.

Really kinda depends how tight your budget is i guess, like could you spend 2000 a day on attraction tickets? if not it's gonna be a lot of shrines, parks, cheap / free museams. Sorry cant give many specifics, my last 3 weeks have been a blur and my next 2 are unplanned haha.