I keep hearing western guys who have just arrived in Japan talking about how much Japanese girls want them
Japanese girls may do any or all of the following things but may have ZERO romantic or physical interest in you:
Lots of smiling and flashing of big eyes
Lots of giggling
Asking you for your email/phone number
Maybe taking your photo with them
Telling you how cool you are
Telling you how handsome you are
Telling you how amazing and strong your body is
(maybe even touching your hair or arms)
They may just be enjoying the novelty of talking to a gaijin, may be just enjoying free English practice or a number of other innocent reasons!!
If they really like you it is possible that you will not know one way or another for months!
Patience and appropriate sincere behavior is essential!