>>11615826DHL just sent me an Import Duty Payment, TL;DR it's $71.80 on top of a 54,850¥ order ($356.05 based on Google's exchange rates right now), not including shipping. So around 20% tariff.
It looks like $18.34 is fixed, $1.34 from regulatory charges and $17.00 from duty tax processing. The remaining $53.46 being based off the 54,580¥ I paid, which I guess maths out to 15% + almost $20 of fixed fees.
Weird part is that on the itemized documentation DHL provided two of the items in the order are missing on the Customs Duty Invoice, but are present on the Commercial Invoice. So either the Duty invoice just failed to list two items coming up to 8,400¥, or maybe those two weren't factored into the customs total for some reason. In the latter case that's $53.46 on top of a $315.63 order, roughly 17%, plus the fixed processing fees and shipping.