I guess my story might be a little different...
I first saw him on an imageboard years ago, with an image I won't post because it violates /tc/'s rules for guro, but it's the infamous bad end CG where Akira confronts him in the rain and it, uh, doesn't go well for Akira. I was strangely compelled by the image, by the look on Keisuke's face, and there was something about him in general that was really appealing to me. Because I was a newcomer to imageboards, though, and didn't understand that images of that quality were likely from visual novels, I didn't go looking for a source.
When I played the visual novel myself when the VN came highly recommended, I fell in love pretty quickly over the course of a week after finding Keisuke attractive, and his personality and history making him even more attractive and perfect to me, but I denied it for about a month before going for it. I've been falling in love with him even more ever since.