oh you mean how Lelouch slept in the same bed as her and never once made a move or even reacted to her lying around in only a shirt and underwear. Stop making shit up faggot. I can believe C.C might have some feelings for him, but sexual tension? gimme a fucking break. Lelouch is hard gay in season 1.
Sexual tension is a plot element employed in works of fiction wherein two or more of the characters sexually long for one another, but the consummation is postponed or never occurs. This longing is often suggested by incidents of intimacy; for instance, when two characters are alone, are physically close, but desire is never explicitly expressed. It also might be suggested in dialogue, as in, for example, a subtle reference to a character's feelings. Sometimes, displays of hostility are used to hide secret attraction, or to deflect true but inconvenient romantic feelings.http://en.wikipedia.org/wiki/Sexual_tension
...So yes. C.C. and Lelouch's relationship in season one is textbook definition of sexual tension.