With Yachiyo in low spirits, Iroha and company leave her behind and head for the Memory Museum. Touka Satomi, a friend of Iroha’s sister, Ui, awaits them there to give them a lecture about the truth of Magical Girls. Yachiyo’s past memories give her a push, and she decides to go find Iroha. However, at that very moment Iroha is already in the midst of a "vicarious practical learning" course prepared by the Magius.

The Magical Girls break into the headquarters of the Magius. After Iroha and Yachiyo reunite, they meet up with Madoka and the other girls, but are confronted by Tsuruno Yui and Mami Tomoe who have become soldiers of the Magius. Mami and Tsuruno, who are being manipulated by another entity, begin attacking the Magical Girls. Iroha and Madoka are in a bind as they are unable to fight back. As a tactic, the Magius summon countless Witches to gather in Kamihama City. The largest ever Supercell is approaching and will hit Kamihama City in six hours. The true identity of the Supercell is actually Walpurgisnacht, the most sinister and evil Witch ever.

It happened in the past… Iroha would go to the hospital daily and play with Ui, Touka and Nemu. The girls loved Iroha and looked forward to her visits. One day, the three girls create an Uwasa similar to an urban legend while playing. That way, if they died, the Uwasa they created would live on and remind Iroha of them. Iroha also created the “Uwasa of Eternal Sakura”, with the wish that the three girls will be discharged from the hospital without illness. And one day... Kyubey appears before Iroha.