Makina, armed with inaccurate knowledge about sex, tries to seduce Eita. However, Eita, inexperienced with girls, is too busy awkwardly trying to be considerate. Sensing a lack of progress, Makina, under the pretense of taking care of him, barges into the bathroom while Eita is taking a shower.

Eita Akutsu begins living together with Makina Agatsuma to help her maintain a normal life without revealing her true identity. Carefully avoiding the watchful eyes of their landlady, the two head to a park where Eita’s close friend Mamimi is waiting. There, they’ve arranged to receive a hand-me-down school uniform for Makina.

Having returned to school life, Makina slips on a banana peel and falls. Eita can’t stop worrying that her malfunctioning left leg might fall off at any moment. Seeing his anxious behavior, Mamimi becomes convinced that he must be a dangerous stalker targeting Makina…

Makina, whose mechanical identity must remain a secret, frantically calls Mamimi from her apartment to explain away the commotion caused at school. During the call, she starts making odd sounds due to Eita's ongoing maintenance, but somehow manages to keep her cover until the end. Just as things settle down, a mysterious girl suddenly appears at their apartment...

Makina loses her body to her younger sister robot, Mimika. According to Makina, Mimika is an agent-type robot skilled at pretending to be fragile in order to manipulate others emotionally. To track down the now-missing Mimika, Eita proposes a strategy only a true mecha geek could devise.

Shrunken down to a tiny size, Makina finds herself in a tense face-off with a now gigantic Mimika. However, she’s unable to make a move—Eita is being held hostage. Mimika threatens Eita, demanding that he perform maintenance on her. As Eita trembles in fear, Makina reveals a secret plan for a dramatic comeback.

After her dramatic comeback victory, Makina points her weapon at Mimika, intending to destroy her. Eita rushes to stop her, revealing his soft-hearted nature. Sensing this, Mimika cunningly seizes the opportunity and shows her true shrewd self. Moved by her act, Eita ends up agreeing to live together with Mimika. Seeing this, Makina becomes jealous and sulks...

Eita continues repairing Makina’s fragile left leg, but thanks to Mimika’s suggestion, they visit a riverside embankment that lingers in Makina’s fading memories. Meanwhile, Mamimi, still determined to take down Eita, encounters a new robotic warrior named Alma…

After their riverside visit, Makina and Mimika return home in a panic—their hair is completely covered in burdock burrs! Meanwhile, Mamimi, now armed with Alma, devises a completely outrageous strategy to utterly defeat Eita.

As Eita and Makina head to school the next day, Makina, thrilled by the improvements to her left leg, can’t stop smiling. But in gym class, disaster strikes—soft tennis is on the schedule! Eita just wants to keep a low profile, but Mamimi has other plans, setting a devious trap that will drag him right into the spotlight…