DNA Says Love You

What if someone you loved from your past whom you perceived as female, comes back as male? Would you recognize them or would they be too different? Would your feelings change or be the same?

ML has a crush on girl in distant past, but meets same person in future and is surprised their gender isn't what they thought it was. Do they realize it is the same person? What is going on? Is the person the same? Does this change ones feelings? Does gender really matter when it comes to love?