Mage's Association members Rin Toosaka and Luviagelita "Luvia" Edelfelt are tasked with finding and retrieving seven Class Cards, medieval artifacts containing the life essence of legendary Heroic Spirits. To aid them in their mission, they are granted the power of Ruby and Sapphire, two sentient Kaleidosticks that would enable them to transform themselves into magical girls and drastically increase their abilities. However, the two mages are on anything but good terms, prompting the Kaleidosticks to abandon them in search for new masters. They stumble upon two young schoolgirls—Illyasviel von Einzbern and Miyu—and quickly convince them to form a contract. With their new powers and responsibilities, Illya and Miyu set forth to collect all the Class Cards. [Written by MAL Rewrite]

Another lovely summer goes by for Illyasviel von Einzbern. Taking a break from her magical girl duties, she enjoys her time off after collecting the Class Cards with her best friend Miyu Edelfelt. However, her break comes to an abrupt end when she and Miyu are abducted by Rin Toosaka and Luviagelita Edelfelt, while out with her friends. The magical girls learn that their work is far from over, as Clock Tower informs them that the out of control mana thought to have been sealed continues to be dispersing throughout Fuyuki City. After heading to the origin point of the out of control mana, Illya and Miyu are tasked with solving the anomaly. But after casting their spell, Illyasviel discovers that she's split into two people! As this mysterious new form darts off, she can only wonder: what is to come from the existence of her dopplegänger, running amok in the unsuspecting town? [Written by MAL Rewrite]

Based on the Fate/Kaleid Liner Prisma☆Illya 2wei! manga by Hiroshi Hiroyama, which is a spin-off of the Fate/stay night erotic visual novel by Type-Moon.

Unaired 13th episode released on the 7th DVD/BD.