オセロ。

Yaya’s high school friends haven’t been very nice. They call her “Yaya the cry-ya! Yaya the misfi-ya!” But no matter how badly they act, Yaya is just too naïve and trusting to believe the worst of her friends. Hard-rocking, butt-kicking Nana is just the girl to grab hold of Yaya’s timid demeanor and turn it upside down. Nana exposes Yaya’s “friends” as slime bags, doles out punishment, and does it all with style. Can there be anything that terminally shy Yaya and hyper-confident Nana have in common? Well, for one thing, they’re the same person... (Source: Del Rey)