Import Taxes and other additional tax

So I am planning on buying a bjd (ball-jointed doll) from Hong Kong and the US (separately). How would I know how much I would pay as tax?

Here are some details:
1) The doll is 80cm made from resin

I occasionally buy handcrafted items from the US (value of USD 200 at most). Sometimes I just receive the parcel with no tax/duty, other times they collect it.

When they collect tax/duty, they seem to apply gsmall-value goods, applicable to simplified rates,h and with that I got charged total of 2,000 yen (breakdown of: 600 yen for customs duty, 1,200 yen for consumption taxes, and 200 yen for customs clearance fee). They seem to make a deduction from the declared value, so that the value they imposed this gsimplified ratesh of 5% on was 12,910 yenc it comes with a detailed calculation.

I just take it that (just as a guideline) I should expect to pay the equivalent of the consumption taxes, 10%, as if I bought it from a shop in Japan.