[Tsuwabuki]

I've done it, and it does depend on the immigration officer. I wouldn't want to do it again. 180 days is a guide, but it really has to do with one of two things: 1) proof of income or 2) proof of intent to leave. If you're rich, you will have zero issues. If you have enough money to prove income for each three month period ON HAND (or with bank statements) you are also fine. The second is much more common, a return ticket. My last time (trip number three), immigration was mighty suspicious. Luckily, I had proof I was still teaching in Korea. I wasn't, I had quit that job, but I had the paperwork saying otherwise. To Japan, it was enough for them to believe I would not abandon a job elsewhere just to lounge around Japan, and thus said paperwork proved I had an intent to leave. When my paperwork for my Japanese visa came up, there was no issue, it was just "oh, you decided to take a job here?" And I was like, "Yep, Korean job knows." "Oh, okay. Great. Here you go." No issue at all.

In the end these restrictions are only to prevent abuse of the social services of the country. As long as you can provide evidence you are not a burden (or working illegally), then you can come in as many times as you want. For most people outside of the fabulously wealthy, this is just not possible to keep on proving.