[Starairi]

I was originally planning to use my own SIM, but now that you mention renting a SIM-card in Japan, what do you know about this?
Is it expensive? Can you call internationlly?
And I've heard that there's quite a long process included in renting SIM-cards/getting a phone in Japan, is this true?

I will be in Japan for 6 weeks, so I suppose I'll use my phone a lot, compared to only staying a week or two.
I also have the opportunity to rent a cellphone there for 500 yen a week (I have to buy air time as well), but I'm just looking for the best/cheapest/most convenient solution.