High school freshman Ranko's sole desire in life is to keep her head down and just get by with as little human interaction as possible. It’s working well, until a random guy is literally hurled into her path (and knocked out when his head hits the wall). The responsible party? A guy she later finds out is her new stepbrother, Kaya Amamine... How exactly is she supposed to live with such a creepy jerk who seemingly has a penchant for violence!?