Nihongo proficiency is not essential to nampa Japanese chicks. I know many womanizers in Tokyo who can barely read a menu, yet meet ladies with astonishing regularity. You should find out for yourself how far a handful of expressions in addition to a lot of gesturing and frisking can take you.
Speaking the language is tremendously helpful because it tremendously raises the amount of girls you are able to hit on. If you don't speak Japanese, you will preclude yourself from a big portion of beautiful Japanese girls. I believe this applies to in any country, but it's especially applicable for Asian countries that have shoddy levels of ESL skills like Japan and South Korea.
As opposed to popular belief, many Japanese women who can speak English nonetheless like to converse in Japanese. An insurmountable, or perhaps simply troublesome, language barrier might be grounds for dumping you. Japanese girls want to at least consider the idea of a prolonged relationship. If you can't connect enough words together to hold up a conversation, that concept becomes more dream than possibility.
If you are not motivated to learn Japanese, an additional factor to consider is that if you don't, you are going to be contending with other lazy gaijin for girls who speak good English. Those are the girls who are very prevalent in foreigner bars, Roppongi clubs, and international parties. Your supply of accessible girls will have a higher percentage of these gaijin hunters if you don't understand Japanese. This may be a condemnation of involuntary celibacy if, like myself, you're a non-white foreigner.
But remember, being bilingual doesn't mean that Japanese girls will come home with you. An underweight (or fat) and poorly dressed man is undetectable to girls irrespective of how many foreign languages he speaks. I ought to know, I was one not too far back.
To close, you don't have to know Japanese to get girls in Tokyo, but being able to will definitely make the process a lot easier. I suggest you start practicing yesterday if you intend on staying in Tokyo for much longer than a few months.
Keep in mind, "can you help me read this " is an excellent pretense for a meeting.
