<p>After quitting baseball because of a certain incident, Tetsuji has been spending his high school days listlessly until one day, his married elder sister suddenly returned home.<br/><br/>She's 188cm tall and he's too scared to ask of her weight. Her name's Mao and her nickname is Maou a.k.a Demon King.<br/><br/>Tetsu is also big-sized but he is timid unlike his sister who is huge in many ways, and they are about to spend an unexpectedly sad yet fiery summer holiday together.</p>
