Hissatsu! Satomi Attack!

In 20XX mysterious creatures "Noum" start to invade the Earth from space. These are virus-like micro-organisms that can turn into various forms depending on affected creature.
Main character attends a his health teacher Natsuki dojo to compete with his childhood friend Satomi. Natsuki is the only survivor of battle with Noum that happened 10 years ago. His extraordinary skills are passed to his students who must oppose new invasion.

[From vndbreview]