Kingdom Hearts.
I introduced a girl to the first game when I was a teenager and, out of curiosity, she bought the game herself. Following that, she got interested in more Japanese games, then by extension more Japanese media, Japanese culture, Japanese art, and is now hoping to become an English teacher in Japan so she can appreciate the art and culture from the inside, rather than a 'grass is greener' approach from the West.
[unrelated self-reflection]
Unfortunately, we since fell out and have cut all ties and are no longer talking, but the last thing she told me was regarding that game. It was sweet and sometimes I wonder what she's up to and how she's getting on, but I doubt we'll ever speak again. Despite nostalgia, she was still a pretty cruel person and I'm sure speaking to her again would only make me angry.
[/unrelated self-reflection]