Iroha remembers that her wish was to cure her younger sister, Ui’s, illness; however, there is no sign of Ui’s existence in her life. She goes to Kamihama City to find clues about her, but is attacked by a Witch and subsequently saved by a trio of Magical Girls, Momoko, Rena, and Kaede. There is a rumor going around about the Friendship Ending Staircase at Rena and Kaede’s school. Momoko and the others believe that a Witch is involved in the rumor, so they’ve been investigating it, but…

Felicia was asked to join the Wings of the Magius, an organization that works within the shadow of rumors. She betrays Iroha and her friends and joins them. Kyoko is also invited by the Wings of the Magius and decides to join the organization. Iroha and company track Felicia down to an underground waterway, where the Wings of the Magius lurk. When the good luck count from the Lucky Owl Water reaches zero, it is said that unimaginably bad luck will befall whoever drank it.

Kuroe lets Iroha get ahead of her while fighting with Magius. Kuroe hears a whisper that puts her in a shock: “Did you forget about me?” At the same time, Iroha is hearing Ui’s voice. Felicia and Sana are confused about Magius’ plan. Sana has questions and explains her intent to Mifuyu, who seems to have given up on everything. Due to the plan, Yachiyo is after Iroha in Kamihama City, which is filled with a large number of Witches. While there, Yachiyo comes across a Magical Girl from Mitakihara City.

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.

The Magical Girls rush to Iroha while fighting against Uwasa of the Soldier Bear. The Amane sisters also stand in their way, but Mifuyu keeps them in check. "The plans of the Magius have failed." Meanwhile, Iroha and Touka regain the memories that Nemu's power took from them. Touka is happy to be reunited with Iroha but can’t recall why they became enemies in the first place. Nemu tells Touka why she had been hiding the truth until now. Now, they see the promise they made with Ui in a new light.