How much is the minimum wage in japan?

How much is the minimum wage in japan?

Do you mean for foreigners in Japan? I'm not sure what the minimum wage for Japanese workers is.
The minimum wage specified for most full-time working visas is 250,000 yen per month. I can't comment on the conditions for part-time or manual workers, and illegal workers are basically at the mercy of their employers with no legal recourse.

Thanks but with that amount, what will my lifestyle be?

Don't be put off by the "minimum wage" label. 250K per month is probably more than most Japanese graduates fresh out of university earn. If you are young and single, it is possible to live quite comfortably on this. If you are older and have a wife and/or kids to support, then it could be rather tight.
Also, it depends on where you live, of course. Housing in central Tokyo is more expensive than in the suburbs or further out in the country.

it should be about 637 yen an hour ($5.30)

It varies by region and industry.

It's 618 yen/hour. It's not what you really "live on".

The minimum wage in Japan is between 750 yen to 850yen and if you work longer on the job it goes more like adding 20yen each year or so. Some companies give extra bonus and provide transportation especially in Tokyo. I think Japan has no tipping system, so I guess tipping in some other countries help a lot for those who just work in low wage jobs.
http://www.cvtips.com/employment/minimum_wage_barrier.html