If you procurar Code Geass in wikipedia, they will show the character list and ofc Lelouch is first then it shows Suzaku then CC then Kallen. I'm not saying that just because of this, CC is the main girl. I'm just letting you know what wikipedia thinks. This is a really hard choice though, but in the end if i had to choose it would be Kallen, she seemed to be mais relatable to and had mais emotional moments than CC in my opinion. There is a different connection i can't describe