Planet Guardian

Koyuki chan is a middle high schooler, kinda coward one. She doesn't like it but she is the chosen one, she has to fight against evil aliens and send them back to their galactical prison. Luckily she's helped by her brother who is a magical girl otaku and by Pirosuke, her guide. This is a funny manga, quite not like other MG ones, adapted from a RPG-like video game.