It's impossible for non-legal resident to get prepaid or sign up for any cellphone service at most stores in Japan. The law requires a legal address and ID verification upon signing up and most stores only take documents released in Japan.
You could go with postpaid services. I believe the b-mobile sim can be found at Yodabashi stores across Japan. But you will most likely need to speak Japanese or find an English speaking staff member to get it
http://www.bmobile.ne.jp/sim/index.html (Data only)
http://www.bmobile.ne.jp/sim_t/index.html (Talk + Data only)
The Rogers iPhone 4S will work in Japan. It will be able to do calls, text and data under roaming on softbank or docomo depending on which network the 4S picks up.
One thing though don't turn off 3G because Japan doesn't have GSM network so even if you don't plan to use data, leave 3G on. Otherwise you won't be able to get any network.
Since I assume the iPhone 4S is locked to Rogers, then you either have to get it unlocked or use another phone that can take foreign sim cards AND have 2100 freq 3G
I'm not sure the purpose of you brother's trip but if it's leisure / vocation then I don't think he will be using the phone much through out the day unless he needs to be connected 24/7.
Also for emergency services in Japan
Ambulance / Fire = 119
Police = 110