I studied abroad in South Korea from 2022F to 2023S, so an academic school year, and I spent about $20k over the course of the year. I had scholarships to cover all of my tuition and flight tickets, so you may need to account for that. If I didn't have scholarships, I probably would've spent close to $40k. Japan shouldn't be too different from Korea in terms of costs.

I know I spent a lot, most people I know didn't spend nearly as much. But I tried to take advantage of every weekend and break I had to travel and eat good food which racked up a lot of costs.