SoftBank SIM rental information can be found here:
http://www.softbank-rental.jp/en/phones/sim3g.php.
The charge is ¥105/day. Outbound local calls are ¥105/minute. Incoming calls are free.
SoftBank rental counters are in the arrival halls of Terminal 1 and Terminal 2.
perfect. this is exactly what i needed. thank you.