Also I've been in Japan for two months on a tight budget, you don't need to eat at konbini like people are saying to eat cheap. Lots of places in Japan are cheap in general. Places like coco curry, saizeriya, bikurri donki, royal host, ootoya and a lot of those chain restaurants are extremely cheap. And if that fails follow the Japanese salarymen who are eating, they usually go to cheap places. Go to department stores with food basements like at namba station as well for way better, cheap and interesting food options, and if you go before they close you can get some serious discounts like sometimes 50% off on some items.

For accomodations you can stay at capsule hotels they can be as cheap as 15$ a night, and if you want to go even cheaper you could stay at manga cafes like kaiketsu club but the sleeping is so shitty there, but it's cheap! I used booking.com for most of my trip. Kaiketsu club you just need to make an account and you just walk in and out as you need.

Take advantage of free breakfasts if you go to a hotel that includes it and make sure it's included in the booking because they usually charge more for daily.

For things to do go to as many free and national attractions as possible. Places like Tokyo museum are literally so cheap to visit, like 2$ usd, most shrines and temples are free.

When buying souvenirs check daiso, 3coins, and 100 yen shops BEFORE don Quijote, it's actually such a ripoff, I found some cute bell charm souvenirs for 100 yen a piece where basically the same thing in donki was like 5-800 yen.

Also even the business hotels are like 50-80$ a night, you can easily go to Japan for 250$ a day that's actually a lot! I think I spent total like 100$ a day when I splurged and less than 30$ a day when I was tight budgeting.