Although many people would not have guessed it, Mokuba worried about his brother a lot. And not just about his safety, his company, his love for him. (Not that way, folks. If you read the summary, this is a KaibaxOC fic.) Mokuba also worried about his brother's future. Seto Kaiba was so cold, even his younger brother could admit. It was a crying shame, really. Seto, being rich, could've made someone happy. But, if he kept on this way, how would he get a girlfriend, get married, have kids? Mokuba had always wanted to be an uncle. But his brother had never had a girlfriend, or even been friends with a girl, unless you counted Pegasus, which Mokuba didn't. Well, not really. It kind of depended on the context.
It wasn't as if girls hadn't tried. Rich girls, slutty girls, fat girls, girls with strange diseases and that one girl with purple skin, who swore that she would go away and leave Kaiba alone if only he would let her have his babies. Kaiba had just shunned them all away (turning the last one over to the MIB). Kaiba was an aloof person. He didn't open up to people well at all. Sure, he was obscenely rich and decently handsome – yeah, no one could/can deny it, least of all you – but the fact that he was a celibate, coldhearted git still remained. This turned all of the other girls off, at least the ones that weren't lusty idiots. (There was a surprising dearth of girls that weren't lusty idiots, however, as soon became apparent.)
This is why he was so shocked when he came home one afternoon to find his elder brother, the Seto Kaiba, playing Mokuba's video games with a girl (and this time Mokuba was sure it was a girl). Especially with one who had lilac colored hair. Or maybe it was the fact that she was hefting a huge yellow mallet and defying the laws of physics at the same time that Mokuba found the most shocking.
Maybe it was the fact that there was a suspiciously neat, suspiciously square, suspiciously 30' x 30', 30' x 30' hole in the side of their living room, as well.