Power Battle Watch Car

Maru's little sister Mari visits the city from her hometown. Mari and Ari are not friendly to each other from first sight. They even have a Watch-Car match against one another, which makes their relationship even worse. Mari makes a lunch box for Ari for make up. At the moment they almost reoncile, Sona, Ari's Watch-Car is attacked by a monster car. The monster car uses the same type of weapon Mari's Watch-Car uses. Everyone doubts Mari as the suspect.