The site linked by Ankur gives the address and website of the Iranian embassy in Tokyo. Guess your friend didn't do his research properly:
JAPAN (TOKYO)
سفارت جمهوری اسلامی ایران - توکیو
Embassy of the Islamic Republic of Iran, Tokyo, Japan
Titel of Diplomatic Office:Embassy
Head of Diplomatic Office:
Date of Establishment:1930
Address:3-10-32MINAMI-AZABU ,MINATO-KU
Address:TOKYO 106 JAPAN
P.O.Box:34489022
Country-Area-Code:0081
Tel.:033 - 34468011-34468015-34468014-34468013- 3446801
Fax:033 - 34462383
Emergency-Tel:
Consular Section:34468021-34468023 FAX CON.3448902
Homepage: tokyo.mfa.ir
E-mail:[email protected]
Online visa applications seem to be down at the moment, but the embassy should be able to help him out. If they say he can't get a visa, I doubt he'll get one by just turning up at some dusty border checkpoint and asking (and if they let him through after paying a few hundred dollars, he's going to have trouble with the first police or other security checkpoint that asks for his papers).