What do you use instead of a HYSA in Japan?

Hi everyone,

I'm currently saving for some house repair stuff (roof replacement, house painting etc) that won't be needed for the next 10 years. Since there aren't any proper savings accounts in Japan, what would you suggest doing instead?

I was thinking of using either an index fund or else wiring the money into my UK savings account, which has something like a 4 or 5% interest rate. Obviously with the weak yen the second choice is not ideal right now. Or I could just put it in the bank, which would be safer but obviously not as lucrative.

Thanks.