Kekeke, Kurimomo and Creayus are two of my favourite artists, pretty much for the reason you stated. They're both really great artists who do those two pairings really well.
C.C. is already drunk and wants more sake (hence: the loose string of her top, she's a bit messed up). Lelouch gets heated, seeing C.C. in this state (blushing, scale raised to the max/turning red). I'm not sure, but is it Lelouch's hand touching C.C.'s right boob?