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.

Miyuki Sawashiroas Reika Hōjō (voice)
Mai Kadowakias Mayu Tsukimura (voice)
Ken Naritaas Mikihiro Tsukimura (voice)
Saeko Chibaas Shinobu Kirishima (voice)
Michiko Neyaas Ryōko Ninomiya (voice)
Junji Majimaas Shungo Ninomiya (voice)
Hiromi Tsunakakeas Irori Okushiro (voice)
Kouki Miyataas Mitsuru Hosaka (voice)
Satomi Akesakaas Hinako Ayakawa (voice)
Koji Yusaas Tasuku Okushiro (voice)
Koichiro Kameyama