20,000yen is roughly enough for a taxi from Narita, I believe there’s some fixed fare taxi services you can book in advance too.
Otherwise you could get the cheaper Narita Sky Access line and take a taxi from the station when you arrive, this route for example. Google maps is excellent for public transport in Tokyo.
Thank you very much. I have seen this page before, and like the price, however it doesn’t say if you can have 5 passengers or not. There is no email contact or live chat, just a phone number…