So this is my history. I'm an international student at Tokyo, Japan. 21 years old, good looking (yeah I know, my ego is big).
Just ended a two years relationship two weeks ago, and become single for the first time in a while. I met a hot girl one month ago at her campus, far from my home, I would say a fair 9, it was like a three-minutes interaction, exchanged numbers and started flirting and though we had a date set for the this week, we ended having the date last week at my place, she was really into me (not everyday a Japanese girl founds a foreigner that speaks really good Japanese) (It resulted she lives really close from my home also).
The date, though improvised (was settled at last minute), was perfect, we cooked together, had a small talk and realized we both have a lot in common, and because I was lazy, ended kissing between the meal and having amazing sex, just one hour after meeting each other, before me building a true emotional bond. After the sex I was amazed, though she doesn't have as much experience as me, the chemistry was so intense, and I felt it the next three days. she had to go because have to catch the last train home. Also, it resulted she was more interesting that I thought, a girl with clear goals for future, from a really rich family, the kind of girl you want to marry or at least have a relationship with.
So till here it was just perfect, but, I just ended a relationship at that time, and because mid term exams forgot totally about cleaning my shit, Facebook (almost never used between Japanese people) and stuff, so after this girl arrived home, she just looked my Facebook and saw my profile picture of me flirting with my ex.
Then I realized I just made a huge monumental mistake x___x ... (her words textually were:
girl: (o_o)
girl: wow
me: What happened? n.n
girl: do you have a girlfriend?
girl answer me
After reading these lines, I realized my mistake, and explain right away I had a relationship that just ended, but hadn't change my stuff, and apologize right away. Then she answered:
girl: No, that's fine. Maybe you have a girlfriend. I'm not mad or anything

girl: Just we should be friends then

Then I replied again I'm single, and knowing there's no point in discussing this point now (you cannot happily win a discussion with a girl), just thanked her for coming and say good night. At this point I was just astonished, how stupid my mistake was, how I probably ended in the friendzone right after scoring (does this even make sense lol) and feeling pretty wear (good because the sex, and bad because how things ended). So after two days of exchanging
just greetings (hello and good night), seeing she is responsive, but making it clear I'm still in her friendzone, I asked her for a coffee, and she said yes but not now because she is busy (that in Japan is a half-yes half-no lol). That in part is true, because the finals are close, and everybody is running to be ready on time.
So folks, thank you for reading till here, I decided will disappear from her radar for a week, until I think my strategy. this is my question, what do you think? What should be my game from now on? what do you think she is thinking? Should I focus in building rapport or keep playing with a playboy attitude?, (I mean, she could easily say I don't want to hear from you again, but saying we should just be friends, means she's still interested right?) thank you beforehand for your comments.