In my experience, if it comes up in the search on global.rakuten.com then they will ship to you directly.
Someone told me I was wrong last time I said that but I still have yet to see anything to the contrary.
If there is a check box that says "use forwarding service" next to the add to cart button then you need a proxy. In this case I would use FromJapan. Just search for the item through FromJapan's website and you can buy it from there.
(The only time I've seen the "use forwarding service" box is by searching on the Japanese site, clicking on an item, and then accessing it through "recently viewed items" back on the English site)
Looks like I was too slow, but yeah what Sev said.
But every time I've done it on the English site they haven't told me how much shipping would be, the just charge it and send it off.
Usually about $15-$25 depending on how big the item is
FromJapan charges 200 yen per item, plus shipping to them from the seller, and bank transfer fees. 200 yen flat is way way better than pretty much every other option (Sutocorp is 8%)