Oneechan ga Kita

The hero is Tomoya Mizuhara, a thirteen-year-old boy at a difficult age whose father decides to marry again. Along with a new stepmother, a stepsister moves into the house: a seventeen-year-old girl named Ichika. The boy's mood immediately sinks, as these twists in his life are far too sharp. Besides, he had only ever dreamed of a brother, ideally a younger one, and instead a real, older sister has dropped onto his head. Nothing is the way he wanted it. Ichika, however, falls in love with the boy, treats him sincerely and tries to help and protect him in everything. Over time the two gradually find common ground, get used to each other and try to support one another.

Ichika is an extremely emotional girl who loves to play to the crowd and draw attention to herself. Whenever she is with Tomoya among her acquaintances, she is sure to brag about her new little brother, while he desperately looks for a place to hide. Tomoya comes to appreciate this attitude and accepts her as a real sister. But things are not so rosy: Ichika starts going crazy over her brother, and her room fills up with photos of him as if she were a fan. Adding to the chaos are her friends, the ultimate sadist Ruri and the busty quarter-Japanese Marina.