Currently the government spends about ¥9.8T on interest expense, which works out to about 1.23% on ~¥800T in aggregate debt. At that level of debt, every 1% increase in the government's interest rate means another ¥8T in expense. This implies that at a 5.2% average rate, interest expense would exceed current receipts of ¥42T.
It's important to note that this analysis doesn't take into account the tenor of the current debt load. Since ¥440T has a maturity of 10+ years it would take some time for interest expense to match any increase in market rates. I also haven't modeled in any changes in the aggregate debt load.