There isn't a whole lot knocking around in Sakuraba Yayoi's head. Maybe she was dropped on her head, maybe she was just born like that; she's a complete moron regardless. Despite her inability to think her way out of a paper bag, Yayoi rose above the odds of her own stupidity and became a Go champion by accident. This has convinced her that she has some sort of hidden intellect, and she adopted a weird new personality. However, she's still a whole lot more idiot than savant.