Shinpei Natsuki is a run-of-the-mill high school boy who just so happens to have a new housemate, foreigner Yuuhou Maria, nicknamed UFO-chan. Turns out she lives up to her name, as she is a Space Patrol Officer sent to Earth to track down the demonic alien species Space Vampiers. Shinpei excitedly joins Yuuhou on frequent trips back and forth in time in her UFO, to prevent the earth from hostile alien takeover, all in the while getting his memory wiped to protect Yuuhou's secret.

In the lower margins is a short strip titled "The Professional" about a hitman sent to take down the mob boss Calpis Souda, with many goofy things happening along the way.