As a teenage male, I see sensei [and the rest of the aikidoka] in my dojo as almost family. Romantic love, though, can cause problems in any previously solid non-romantic relationship. The question of jeopardizing a good friendship for the risk of something 'greater' is one that is far from rare among male/female friendships.
Unfortunately, there's no definitive answer.
I've experienced situations that went both ways, and know many people who would advise to "back off" and play it safe, and many who say go for whatever you feel.
I urge you, ironically, not to let the comments in this thread guide you. Use them, instead, like a coin toss. Don't go by which side turns up, but by your emotional reaction to whichever choice chance chooses.
If you read a response in this thread urging you to stay away, but in your heart and head you feel the urge to skip or disregard this comment - there you go.
If this is about ruining a teacher/student relationship, though, I suggest you persue romance. It's indeed possible for that relationship to continue. At my dojo, Sensei's wife practices with us. On the mat, she calls him sensei. Off the mat is a different story, of course.
Either way, good luck!
(and thanks for all of your time)