http://www.andriasang.com/e/blog/2010/09/11/catherine_katherine/    

 Here's a screenshot showing how it might have happened:   Lol 

Created a character page for Katherine. Still very excited to see how this game turns out!

Not much info about the plot, but at least we know who Vincent's girlfriend actually is now.

Screen shots from Famitsu: http://www.famitsu.com/news/201009/images/00033165/yLh6hf5PAfK99MbAAn68R98yZ8fO67tQ.html 
Also additional info: http://scrawlfx.com/2010/09/catherine-meet-vincents-girlfriend-katherine

Seem like Main Character has a fetish for girls who have similar sounding names

This is turning into a dark-ass episode of Three's Company. Also I'm reminded of Cathy and Kathy from Kids in the Hall.

After playing Persona 3 and watching the Persona 4 endurance run I really just want Persona 5... I'm sure this game will be great, Atlus tends to put out quality titles and I will probably check this out if it comes to North America, but I just want P5.

I'm gonna go out on a limb and say that I think Catherine with a C is just some kind of sexual manifestation of Vincents mind since he's fearing the thought of fatherhood. My only basis for this is the fact that you dont name two main characters pretty much identically without real reason, and her hair is in the same style as the horns of those creepy ass rams. Or I'm just crazy.