Alien Nine

Alien Nine (エイリアン9, Eirian Nain) is a manga series by Hitoshi Tomizawa, which was later adapted into an anime OVA series by J.C.Staff. The manga was serialized in Akita Shoten's Young Champion magazine. In 2003, Tomizawa released a 1-volume sequel to the series called Alien 9 Emulators.

Plot
Yuri Otani, a rather melancholic 12-year-old, has just arrived in sixth grade and has (begrudgingly) joined the "Alien Party", a team whose primary objective is to capture any otherworldly aliens that may appear on campus. To make matters even worse for Yuri, the only way that capturing the aliens can be made possible is to adjoin with a "Borg", a symbiotic life-form whose sole purpose is to protect their host, incapacitate, and ultimately capture other aliens, using anything available to their arsenal (which includes, but is not limited to: Borgs, inline roller blades, knee pads, and lacrosse sticks.) Yuri is not alone in her tribulations, for she has two other Alien Party member friends - Kasumi Tōmine and Kumi Kawamura.