Here's a link to the schedules for the Narita limousine bus:

http://www.limousinebus.co.jp/e/time...ex_n/tcat.html

Apparently, the last bus leaves at 23.00. But I'm sure you can catch the one leaving at 21.45 or 21.55...

Tokyo is definitely more expensive than Hong Kong and Singapore. I would disagree that Hong Kong is the cheapest of these three Asian cities. Singapore is the cheapest in my opinion. Take a look here:

http://www.finfacts.ie/costofliving.htm

Tokyo is a very, very safe city. People are more than willing to help you when you ask and will often go above and beyond what you asked for.