Yuusei Shonen of the Space Patrol

A vast shadow has fallen over the planet Earth in the "far-off future" of 2001. The shape-shifting Zygons, one of the most hated species in entire the galaxy, have begun infiltrating human society via its smallest and most defenseless members: young children.

While this secret invasion goes unnoticed by most of humanity, The Supreme Galactic Council has sent its greatest warrior to deal with the Zygon infestation. Armed with the power and technology of a thousand worlds, Yuusei Shonen undertakes the most important mission of his career - to protect an entire planet from the most dangerous creatures in the universe.

His orders are simple: hunt down and exterminate the Zygons before they can breed. Failure is not an option; if the aliens manage to propagate, The Galactic Council will be forced to destroy the entire solar system.

The fate of the Earth is literally in Yuusei's hands - but how can he even hope to succeed against such a devious and dangerous enemy? 

Well, the first step is to inspect Keiko's underpants, followed by every other girl in her class.