WACC real rate calculation

Hello Everybody! Could you please help me with a discounting rate issue? I'm working on an investment project with 60% leverage. Let's say nominal cost of equity 15% (Russian rubles), and cost of debt (jpy) is about 3.5%. Tax shield 20%. Then my WACC will be calculated as 15% x 0,4 + 3.5% x 0,6 x (1 - 20%) = 7.68%. Now, I need to calculate the real discounting rate and there are some difficulties: Russian inflation rate is about 4%; Japanese inflation rate is about 1%; I can't simply subtract a corresponding rate from the debt cost, because there will be a mistake in a tax shield calculation. Should I subtract only Russian inflation from WACC (Russian entity) or subtract weighted inflation rate from WACC?

Thanks!