Yuri Otani who just moved up to the sixth grade was melancholic because she was forced to belong to the post that she never wanted to belong. The name of that post was "Alien countermeasure team". The work of the team was to capture the another world's creatures which fell one after another in their school, and to defeat them. That was dangerous and hard work. They had to attach symbiosis type alien to their head to increase their power. That was unpleasant, and Yuri hated this work.
This is the SF anime in which the activity of three girls of alien countermeasure team at the near future school "The ninth elementary school" is described.