Where are you calling from? Inside Japan or outside? Here's more info on how to call Japanese phones:

City codes [area codes] are not defined about phone numbers beginning with 0_0 in Japan.
If he surely has a cell phone of Japan, its number has eleven digits and begins with 090, with 080, or with 070.
Eleven-digit numbers beginning with 050 are for IP phones, not for cell phones.

If his phone's number has ten digits and begins with 0981, 0988 or 0989 then the phone is a fixed phone.
098 is the area code for the area including Kadena Town, Nakagusuku Village and Naha City, but you can omit an area code only when you call from a fixed phone in the same area.

//

Sorry, why do you think you need to figure out the city code to call his cell phone?

If the OP's fiance is at Kadena then they are probably Americans, and US cell phones have area codes and look like regular landline numbers.

Kelly,