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.

Undaunted by the spanking received from Natsume last night, Yuu steals out of the house early in the morning in order to test her powers as Creamy Mami; while Yuu admires herself as Creamy Mami, Nega and Posi get into a divergent concourse over who is to blame for Yuu successfully sneaking away when Mami decides to drop in for a visit to see if Tetsuo and Natsume can recognize her before flirting with Toshio as she leaves. Meanwhile, Shingo Tachibana is dismayed to have it explained that Megumi Ayase and her manager Hayato Kidokoro are stuck in traffic along with finding that he has to resolve all the office politics caused by such a development until he encounters Mami walking around; a whirlwind of customization and instruction later, Creamy Mami is enjoined for a song whose lyrics the host withholds from her. Even if Creamy Mami successfully improvises a song and escapes the stampede of her newfound fans, Yuu is still stuck with a lengthy home commute whose resolution ultimately requires Toshio as a deus ex machina -- after Creamy Mami admonishes Toshio to behave dignity and respect unto Yuu.

Toshio's efforts to temper Midori's expectations of spending time with Yuu obfuscate the fact that Yuu herself is grappling with the disadvantages of being Creamy Mami -- the greatest of which is the narcissistic and fanatical Shingo Tachibana hell-bent on making Mami a star with his company as he orders his staff to find her. The panic Yuu is driven into at the sight of Toshio explaining Shingo his recent encounters with Creamy Mami while Midori tries to steal lustful glances at her illustrates the immense contention that Yuu undergoes as she tries to keep her double life as Creamy Mami a secret although Tetsuo and Natsume are picking up some piecemeal clues; nevertheless, Yuu unwisely decides to »debut« before Toshio so that she can explain things and nudge him toward the rest of his life but is shocked to find that Shingo has other ideas and is not taking no for an answer. Facing the backdrop of Shingo and Megumi ultimately having made the choice for her, Creamy Mami begins her career at Parthenon Productions in earnest.

Toshio pays the peckish Midori a visit to entreat his company to a Creamy Mami concert that gives way to the contest for who gets a date with Mami; for Toshio, Shingo has already polluted the lottery. When Yuu offers it to him as a consolation prize, Toshio laughs at her and suggests that Midori would be better suited for such a thing; while Midori agonizes over what he should do on a date before asking Mamoru for help, Posi picks up on how Yuu is having second thoughts with dating Midori and is in anguish over how she always quarrels with Toshio. Zero hour for the date finds that both Toshio and Mamoru are uneasy about how Midori will do on a date with Yuu; sure enough, the date has barely begun and their anxieties are already proven not unfounded. Midori being quite the gentleman to Yuu who enjoys his company ultimately does not supersede that Yuu would much rather spend time with Toshio because of their prologue together; Midori comes to grips with the fact that the most mileage he will attain with Yuu is the big brother-little sister kind of love.

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.