Good Luck! Ninomiya-kun

Overview:

Ninomiya is an ordinary high school student who lives at home with his older sister Ryoko. However, Ninomiya's life ceases to be normal the moment a cute girl named Mayu descends into the middle of his school's campus in a military-grade helicopter. It turns out Ryoko sent this girl, along with her older brother Mikihiro, to live at the Ninomiya household.