This post has nothing to do with Roppongi. Although, with a title such as "The Gates of Hell," it certainly could be!
Actually, Jigokudani Yaen-koen (eng: The Gates of Hell) is a small valley with onsen, near the site of the 1998 Nagano Winter Olympics. It is famous for Snow Monkeys! These small macaque monkeys spend most of the year in the forest, but during winter, about 250 monkeys take over the outdoor onsen. Apparently for warmth, as well as for nearby food supply.
Warnings given prior to visiting include: do not eat near the monkeys, and do not even have food on your person! The monkeys can sniff it out and will attack! Uhm, I'm not sure if I am scared of monkey attack...these guys are not too big. Although, I'd like to avoid a nasty infection.
Another warning, do not make direct eye contact. WTH? Do not make direct eye contact with the monkeys?! Are they the Queen?! It is mentioned, "if a monkey makes eye contact with you, look away quickly."
Regardless of the potential of monkey attack, I hope to go on an excursion to see them on 12/23. (A holiday dontcha know! Emperor's Birthday.) I must scurry over to the bank to make my payment before all the spots are gone...
Upon consideration, the above warnings are also appropriate for the other "Gates of Hell" i.e. Roppongi. Do not carry food on your person or it will be sniffed out. Do not make eye contact with the minions loitering along the street. If you notice one of them has engaged in eye contact with you, look away quickly!
Unfortunately, looking away quickly does not work well in Roppongi. They will follow you anyway. All you can hope to do is quickly find a refuge to duck in to, hide out a moment, and hope their short attention span puts them on anothers trail.