The story begins with our heroine Yuu Morisawa watching the Feather Star descend for a landing oblivious to the hefty workload at the crepe shop that her parents Natsume and Tetsuo are desperately trying to resolve on their own; a clumsy stumble into her childhood friends Toshio Ootomo and Midori Kisaragi later, the panicked Yuu votes with her feet using Tetsuo's scooter into a frenzied pursuit sequence whose zenith is four police cars and a helicopter along with Toshio on a bike. Oblivious to the chaos that she has caused with her mad dash through town, Yuu is enthralled with the Feather Star as it comes in for a landing; upon learning that she can see the Feather Star, the two alien cats Posi and Nega draw Yuu aboard where there is a dysphoric fantasy dream sequence that gives way to an encounter with the grateful alien Pino-Pino. Having some family government imparted at the breech upon arriving home sets the stage for the ultimate silver lining of Yuu finding that Natsume and Tetsuo are not hostile to housing the two alien felines who later lead her through utilizing her new-found magical powers; after some cryptic and perplexing trial and error, Yuu successfully initiates her first henshin into Creamy Mami.

The hysterical frenzy over Creamy Mami's debut song evenly divided between people buying the album and converging on the upcoming concert obfuscates that the magical idol is actually Yuu Morisawa effecting the mirage of being infirm -- although she almost blows it at the mention of her favorite dish. Yuu finds that the successful concert at Parthenon Productions as Creamy Mami does her no good against Natsume's zeal to impart her maternal perspective on her subterfuge or the impromptu test for sleeping in class; if those problems are not enough, Toshio's teasing and a collision into Midori costs Yuu her compact right when she is going to need it the most. Yuu's frantic search for the compact gets a big boost from Toshio explaining that Midori at the amusement park has it; while she successfully conquers the high-stakes aerial adventure necessary for its retrieval, Yuu ultimately ends up igniting Megumi's vendetta of Creamy Mami.

While Hayato and Shingo compare notes with Megumi about whether Creamy Mami will be punctual for an advertisement filming in a wilderness area reputed to have a black stag that has been visiting unto the locals bad luck, Yuu daydreams about being on a date with Toshio cured of his Creamy Mami addiction but causes a misunderstanding on the train when she speculates out loud Toshio and Midori's hidden motives for the outing; during the bus ride from the train station, Nega and Posi compare notes about the legend describing a magical stag that once resided on the Feather Star along with the pros and cons of emancipating the mystical ungulate from its subterranean prison. The astonished adoration of the black stag quickly gives way to it being time for Yuu to do her thing as Creamy Mami. The black stag's risky shortcut whose zenith is being trapped on a high rock ledge has the ironic silver lining of ultimately being the commercial Creamy Mami is to have done originally; now his former golden normal-sized self, the stag explains Mami his prologue and leaves behind the capability to manipulate the environment as he returns to the Feather Star.

The approach of a Category II typhoon becomes the forum of an anxious Natsume forcing the reluctant Tetsuo into an impromptu honey-do list of emergency home repairs while Yuu teases him at school commute inception; while Yuu divides her energies between the school commute and splashing through the puddles along the way, Shingo and Hayato are discussing the commercial that afternoon involving Creamy Mami when Hayato goes into a story of how there are ghosts in the studio where Megumi demonstrates some of the disadvantages of showbiz. Yuu's school cuts classes short because of the typhoon which affords plenty of time to rush to the studio where an unscrupulous news reporter named Snake Joe takes advantage of Megumi's disgust with the office politics by killing the electricity in the building; neither gets very far when a ghost panics them into fainting. It ultimately falls on Yuu to save the day by photographing Megumi and Snake Joe red-handed in the generator room prior to restoring the power; Yuu's heroism does nothing to save from being in very choppy water with Natsume and Tetsuo being anxious for her safety.

While evading the wrath of the frustrated production staff for interloping onto the production set and leaving a trail of destruction as she is being chased around, Zashikiwarashi searches around for another playmate before settling upon Yuu who is having a blast. While the mythology associated with Zashikiwarashi expounds upon her bringing happiness to the homes she visits, such is a long way off when Zashikiwarashi shows up the adults who then give chase after her although Zashikiwarashi herself means no harm and has not a mean bone in her body -- not with how she behaves toward Posi and Nega along with enthralling the kids with her charisma. Galvanized by Zashikiwarashi's prologue of boredom and loneliness, Yuu lends Toshio and Midori as surrogate friends as she decides that an engagement with Creamy Mami is in order -- a decision easier said than done with having to retrieve the wand which appears out of reach. True to Hayato's anxious admonition, Zashikiwarashi does act out her impatience for Creamy Mami which interferes with the show but also has the ultimate ironic silver lining of celebrating Megumi who has been marginalized in favor of Creamy Mami.

The ambiance is intense as the audience awaits Creamy Mami's arrival so that the concert can get underway; upon seeing the audience population tabulation, Shingo is overjoyed as he recalls his entire prologue with Creamy Mami who wishes a solo concert much to his shock as he wonders why Mami feels the need to rush her professional career. The frustrated Megumi ironically becomes the deus ex machina that enables the concert to begin in earnest; amid short-circuiting electrical equipment that gives Shingo cause to suspend the concert, Creamy Mami sings with everything she has even though she knows the outcome along with Posi and Nega as Toshio feverishly searches for an apparatus to test his hypothesis that Yuu and Creamy Mami are one and the same. Just as Mami prepares to sing the final song, the Feather Star's descent for a landing clearly visible to everybody sets the stage for Mami to have explained to her that the deal is over especially since Toshio has remembered everything. After contributing special effects to complement Mami's final song as a final parting gift, Pino-Pino gets underway with Posi and Nega as he tells Yuu he is not hostile to an occasional visit before depositing her right where Toshio can escort her home.