Buying a pre-paid mobile phone in Japan

So basically, i lost my phone in december - which just shows how unlucky i am because apparently, you can't lose phones in japan (because they are really good at returning things) but yet, i did!

I think I will be in Japan for another 6 months so I don't want to sign up to any 2 year contract. (paid 40,000 yen to AU for losing my phone, that was painful) Im looking at unlocked phones and I found one I really like on Expansys.

Is B-mobile the best way to go? Tbh, i don't know whether I want to give them my card details as it makes me feel a bit eeky. I would significantly prefer widely used companies like softbank or docomo (don't wanna go back to au, they were horrible when my phone was gone). Any plans there that you might recommend?

Also, if i do go with b mobile, is that a contract too? I don't know for sure how long I am actually going to be in japan so I don't want to be obligated to anything.

It's not iphone that I found on Expansys, (wish i can afford iphone 5s though, really wanna try that fingerprint recognition thing) its LG Optimus L7 Dual P715 (unlocked of course).

unless you understand japanese or have a japanese friend, online contract with bmobile is difficult
so, softbank seems a good choice

bmobile

plan name:スマホ電話SIM フリーDATA(smartphone talking sim with free data)

talk:1560jpy/month+20jpy/30sec

data:free but slow(200kbps)
data option:1560jpy up to 3GB(no speed limit)

contract:5months(penalty:8000jpy)
online contract

credit card and residence card are needed

no English webpage


softbank
plan name:prepaid smartphone

talk:0jpy/month+9jpy/6sec(45jpy/30sec)

data:7350jpy/30days(no speed limit)

your phone should have a technical comformity mark
http://www.tele.soumu.go.jp/e/adm/monitoring/illegal/monitoring_qa/ind...

softbank web page
http://www.softbank.jp/en/mobile/price_plan/prepaid/