Uiba Shikatani, the daughter of a pet shop owner, harbors profound emotional ties to animals. Her grief over unhatched reptile eggs leads her father to offer an enigmatic striped egg, which cracks open to reveal a green dinosaur capable only of echoing "Muka Muka"—a name born from its singular vocalization. As the creature’s dedicated guardian, their inseparable bond anchors numerous escapades.

Her childhood circle includes Hazuki, a determined first-year junior high student dubbed "Moon Sister" for her fierce loyalty in defending friends and confronting rivals. Alongside Senta, they navigate everyday life within their bustling shopping district community.

A defining moment arises when Uiba’s actions draw sharp criticism from loved ones, sparking introspection. Personal nuances, like her September 13 birthday and blood type B, occasionally surface. A harrowing nightmare blurs reality until exposed as illusion, delving into psychological complexity.

The striped egg’s true origin—crystals instead of life—unleashes collective astonishment, underscoring unpredictable turns. Collaborations with a professor’s inventions, including a time machine, thrust Uiba into prehistoric realms through temporal rifts, challenging her innate curiosity and adaptability amid extraordinary trials.