"Mojacko" is a comedic manga series centered around the misadventures of a quirky alien family living on Earth. The story revolves around the Mojacko family, who hail from the planet Mojamoja. After their spaceship crashes on Earth, they decide to settle in a small Japanese town, blending into human society while attempting to repair their ship. The family consists of Mojarin, the mischievous and energetic younger brother; Mojako, the older sister with a sharp tongue and a knack for technology; and Mojappa, the laid-back and often clueless father. Their mother, Mojami, is a caring but eccentric figure who tries to keep the family in line.

The narrative primarily focuses on the family's daily life as they navigate the challenges of living among humans while concealing their alien identities. Mojarin, the most prominent character, often causes chaos with his impulsive behavior and curiosity about Earth. His antics frequently lead to humorous situations, such as accidentally revealing his alien abilities or getting into trouble at school. Mojako, on the other hand, serves as the voice of reason, using her intelligence to solve problems and cover up her family's mistakes. Mojappa and Mojami provide comedic relief, with Mojappa's laziness and Mojami's over-the-top reactions adding to the series' lighthearted tone.

Throughout the series, the Mojacko family encounters various human characters, including their neighbors and classmates, who often become unwitting participants in their escapades. The interactions between the aliens and humans highlight cultural differences and misunderstandings, creating a blend of slapstick humor and situational comedy. Despite their extraterrestrial origins, the Mojacko family's struggles with everyday life—such as school, work, and relationships—make them relatable and endearing.

The manga maintains a episodic structure, with each chapter presenting a self-contained story that contributes to the overall comedic tone. While the primary focus is on humor, the series occasionally touches on themes of family, friendship, and acceptance, as the Mojacko family gradually forms bonds with the humans around them. The lighthearted and whimsical nature of the story, combined with its quirky characters, makes "Mojacko" an entertaining and accessible series for readers of all ages.