Coming from Germany, Sweden is already expensive to me. So I would say Japan is slightly more expensive, but in different areas compared to Sweden. Food is cheaper, local transport is much more expensive (no student tickets or monthly passes!).
I received the JASSO scholarship from Osaka University of 80.000 JPY (= 6.400 SEK) per month, so this made things much easier. The scholarship is given to you when the funding is available, no extra application is necessary, it’s just a box you tick during the formal application to Osaka University.
Also, there is a scholarship from the Sweden-Japan Foundation. The deadline for it is in March, you can apply without an acceptance letter. Apparently students usually get some funding here, but not me. Maybe you have to be a Swedish citizen for this or my application in Swedish contained too many weird mistakes since my language skills are rather limited. Who knows. It’s worth a try though, but you have to be quick with the deadline.
KI provides free medical insurance for the whole stay (it doesn’t cover trips to other countries though!), however you will still have to sign up to the national insurance in Japan. This happens at the city hall when you register your residence card. The invoices are the sent to you by mail and you can pay them at any convenience store. For me, it was 2.500 JPY per month. The insurance contract is made for the time your visa lasts. This was six months in my case, but I only stayed for four. You can simply go to the city hall again and cancel it before you leave. I was also told to sign up to the national pension plan and received some letters (in Japanese) about this, but never did it. Wasn’t planning to receive any form of retirement subsidies so I didn’t do it.
I bought a return ticket with Emirates from Munich to Osaka Kansai KIX. Itami Airport, which is also called Osaka International Airport, doesn’t have a single international connection. It’s a trap. Make sure to state the right one in the visa application, I was fooled by this. My ticket was 850 € and surely not the cheapest option, but I wanted to do a stop-over and stayed three days in Dubai on my way to Japan. I can recommend doing this, it’s usually not much more expensive. Istanbul, Singapore, Seoul, you name it, just depends on where the airline hub is. KI gave me 7000 SEK as a grant (INK) which almost covered the ticket.
The public transport is a bit annoying around Osaka Uni, which is why I bought a used bike for 11000 JPY. This saved me a lot more money in return, and I even could sell it at the shop again before leaving.
In general, the JASSO funding provided for living and housing, and the money I usually have came on top so overall my financial situation was more than ok.